Which is the best iPhone voice control technology? And which is the best Mac voice control? Which mobile platform - or speaker setup - offers the best voice control technology: Siri, Cortana, Google Now or Amazon Echo's Alexa?

Siri has made a lot of progress in the last couple of years, developing into an impressive digital assistant that can handle all sorts of tasks on your iOS devices, on the latest Apple TV and - once macOS Sierra launches in the autumn - on Mac as well. This last step is long overdue: Siri's absence on the Mac has been a glaring omission for years, especially as Microsoft has had its own Cortana voice-tech running on Windows PCs since the launch of Windows 10 last year. You can use Cortana on the latest Lumia Windows phones too, and there are other rivals lining up against Siri as well.

Google has had a voice-search option built into its apps for both Android and iOS for a while now, along with built-in support using the Chrome web browser. Amazon recently launched its new Echo speaker system that includes the Alexa voice-assistant. The Echo is only available in the US at the moment, but we spent a few days recently with the new iPhone SE, Windows Lumia 950 and the Google app to see how the various voice assistants coped with a variety of requests and commands.

So there's a lot of voice assistant activity around, but Siri is still the one to beat (at least for Mac and iOS users). We decided to test out Siri and all the other options on the market.

Updated, 17 August 2016, with additional reporting by Lou Hattersley.

Best iPhone voice control: Siri vs Google Now vs Assistant.ai vs Viv

Voice Assistants for iOS

When it comes to the iPhone and iPad, there is some considerable pressure on Apple's Siri.

Google Now

For a start, Google's own voice assistant, known as Google Now, is found inside the Google Search app and Google Chrome web browser.

Between the two apps you can replace much of Siri's functionality on your iPhone. In our experience Google Now is better than Siri at voice comprehension for basic search terms, such as "What is the capital of Mozambique?" and "What movies are playing at the Prince Charles cinema?"

But Google Now falls down on integration. Asking Google Now to create a reminder or send an email sometimes bounces you to Gmail or Google Calendar, but it never fills out the detail from your voice message. Sometimes it simply searched for the phrase, returning Google results for "Set a meeting for 2pm today".

Assistant.ai

There are voice assistant options beyond Siri and Google Now. Assistant.ai is a popular option on the App Store. It's a free download, but you need to sign up for an account (or link it to Facebook or Google).

Visually, Assistant is a bit cheap and cheerful. While Siri blurs the screen and Google Now has a circular fade effect, Assistant displays a female clip art character holding a laptop.

The voice is much more mechanical than Siri or Google now, and while Siri's quirks are charming, Assistants are a tad odd. Maybe it's the techno-voice, but a robot saying "top of the morning to you" just struck us as weird.

Viv

Viv is a name to look out for. Viv is in development for iOS and is being created by the same team that made Siri (and then sold it to Apple). A video demonstration by the makers in May demonstrated a lot more complexity than Siri. Questions posed by the Viv team included things like "Will it be warmer than 70 degrees near the Golden Gate bridge after 5pm the day after tomorrow?"

Three months on and we still have no idea when Viv is coming out. But when it does we will may have a solid rival to Siri on the iOS. Then again, many of the impressive features of Viv, such as stackable enquiries (questions that you ask can relate to previous questions), will be in Siri along with the iOS 10 update. So it may be that Apple and Viv are racing to improve voice AI (artificial intelligence) and will be neck and neck when Viv is finally released.

Read more: Meet Viv, the new voice assistant from the creators of Siri

Best Mac voice control: Siri vs Google Now

Siri for Mac

One major facet of the macOS Sierra update is the long-awaited presence of Siri on the Mac. Holding down Command-Space in macOS Sierra brings up a Siri alert box, enabling you to ask questions, respond to messages and emails or create calendar events and reminders on your Mac.

We've looked at Siri in depth in macOS, and it's proving so far to be a major boon to the operating system.

Read more: macOS Sierra release date UK

Google Now is available as part of the Chrome web browser, and you can even access it using a keyboard shortcut: Cmd + Shift + . (that last one is a full stop).

Where Google Now on the Mac has the edge on iOS is with integrated functionality. You can create reminders and add events to Google Calendar using Google Now search inside Chrome. So if you're heavily invested in Google services it's well worth testing out what you can do with Google Now.

On the Mac there is also the much more professional option of investing in Dragon for Mac. It's created by Nuance, who power the voice recognition technology behind Siri. At £139.99 it's not a cheap option, but it is championed by people with limited typing ability who use it to dictate messages. It has powerful editing tools, and can be used to completely control your Mac.

Read next: How to fix the most common Siri problems

Siri vs Microsoft Cortana vs Google Now vs Amazon Echo

Amazon Echo - only available in America at this time

Best voice control tech: Siri vs Cortana vs Google Now vs Amazon Echo - Understanding regional and foreign accents

Siri was the butt of plenty of jokes when it was first launched, but voice-recognition technology is constantly being refined so that it can deal with a wide range of voices, as well as national and regional accents. In fact, accents from different countries don't seem to be too much of a problem for these voice-recognition systems any more. The Amazon Echo is only available in the US right now, but Siri, Cortana and OK Google are used on smartphones sold all around the world, so they have to be able to cope with a wide range of accents.

Read more: Can Siri cope with British regional accents?

If you've got a really strong regional accent, or something like Dick Van Dyke's legendary cockney accent from Mary Poppins then you might get the occasional "Sorry, I didn't catch that." As it happens, I am a genuine cockernee myself, and it was only OK Google that understood my exaggerated "Cor blimey, guvnor!" when I tried a Dick Van Dyke impression as a test.

However, these voice systems are designed to learn and recognise your personal accent and speech patterns as you use them day after day, so it's only the most extreme accents and dialects that are likely to cause any problems.

Best voice control tech: Siri vs Cortana vs Google Now vs Amazon Echo - Dealing with natural language questions

Reverting from Dick Van Dyke mode to my normal speaking voice, I found Siri to be one of the most versatile voice-recognition systems, and it was able to field all sorts of questions, from just asking about the weather to finding a nearby petrol station or looking up flight times on the internet. And, importantly, Siri is also very good at dealing with colloquial language, which makes it feel natural and easy to talk to.

Apple's programming team have obviously had a lot of fun figuring out how Siri can respond to remarks such as "Hey Siri - how's it hanging?" (response: "I'm happy to be alive!"). But when I asked Cortana and OK Google that question they both ended up doing a web search to look up the derivation of that phrase in a few online dictionaries.

Best voice control tech: Siri vs Cortana vs Google Now vs Amazon Echo - Breadth of knowledge

Siri isn't perfect, though, and seemed to be completely stumped by my request for "film times at the Rich Mix cinema in Shoreditch" (a well-known hipster hangout in East London). In contrast, Cortana and OK Google took this in their stride and quickly found the film times on the web for me.

Oddly, though, Cortana could sometimes be completely thrown by a relatively simple question, such as "What day is it today?" That enquiry left it beeping and repeatedly telling us that that it was "thinking" until the Lumia phone turned itself off after a couple of minutes.

One other difference worth mentioning is that Cortana and the Google app both attempt to anticipate questions that you might ask and provide information automatically. Cortana stores a 'notebook' of topics that you're interested in, while the Google app creates a set of 'cards' on similar topics.

This allows them to automatically provide quick updates on the weather, share prices and other information without you needing to ask, whereas Siri just waits until you specifically ask for something first (although the iOS Notifications system can update important information for you as well). 

Siri vs Microsoft Cortana vs Google Now vs Amazon Echo

Siri on Apple TV - gain control of you TV while sitting in your favourite chair

Best voice control tech: Siri vs Cortana vs Google Now vs Amazon Echo - Running and activating other apps

Another strong point of Siri is that it's designed to work with other Apple apps, such as Mail and Reminders, so you can tell Siri to "Send an email to Cliff" and then even dictate the entire email to your iPhone. That's great when you're driving, or in other situations where you're unable to use your hands, and some cars that support Apple's CarPlay software even have a special Siri button on the steering wheel so that it's always available without taking your hands off the wheel. 

Google is also getting in on the driving scene with Android Auto, and if you're using OK Google on an Android phone then it can work with other Android/Google apps to send emails, create reminders and perform other tasks just like Siri. However, depending on the type of phone you have, you may have to activate OK Google from within the main Google search app, rather than being able to activate it from the Home screen as you can with Siri. The iOS version of the Google app is a bit more limited, though, primarily using its voice option for web searching rather than being an all-round digital assistant.

Cortana is also good at working with other apps on Windows devices, and had no trouble creating emails, reminders or notes. We could also use it to launch other types of apps too, such as the Paint graphics app on a Windows laptop, although we were a little disappointed to see that Cortana couldn't handle additional commands, such as pasting a screenshot into the app for us. Even so, Cortana is the only one of these digital assistants that currently works well on a wide range of desktop and laptop computers, as well as mobile devices.

In fact, Microsoft has even launched a Cortana app for iOS (although this is currently only available in the US). That's really throwing down the gauntlet for Apple and Siri, and makes us even keener to see Apple bring Siri on to the Mac as soon as possible.

Best voice control tech: Siri vs Cortana vs Google Now vs Amazon Echo - Switching on accidentally

Speed and accuracy of response isn't the only thing you need to think about. The Amazon Echo recently made the news when a number of owners reported that the Alexa assistant was responding to voices it heard on the television - starting a music playlist unprompted, and even adjusting someone's radiator thermostat in one case. 

But that's been a problem for Siri too. When Apple VP Phil Schiller introduced the new iPad Pro there was a point in his speech where he was talking about using Hey Siri - except that he pronounced it "Hey... Siri" - and admitted that he did this in order to avoid activating Siri on iPhones belonging to people in the audience. He was joking, but there was more than a hint of truth to the jest.

We tried Siri out with some videos from YouTube (check out the popular "Siri, call my girlfriend" clip) and it did sometimes respond to voices coming from the speakers on our office iMac.

How to stop Siri, Cortana and Google Now from responding to other people's voices

Siri has an option that allows you to train it to so that it can respond more selectively to just your voice. Go to Settings/General/Siri and then turn Hey Siri off, and then on again. This prompts you to repeat a number of phrases so that Siri can learn to recognise your specific voice, and once I'd used this on my iPhone I found that Siri no longer responded to any voices other than my own. 

Cortana provides a similar training option, but it also includes an option that allows it to respond 'to anyone' - perhaps if you're using it on a tablet that you share with other members of your family. You can train OK Google too, and some of the latest Android phones also allow you to create a profile for a 'trusted voice' that can be used to give commands even when your phone is locked. 

Siri vs Microsoft Cortana vs Google Now vs Amazon Echo

Cortana is available for Windows desktops..

Siri vs Microsoft Cortana vs Google Now vs Amazon Echo

.... and Windows mobiles.

Best voice control tech: Siri vs Cortana vs Google Now vs Amazon Echo - Which is fastest?

One thing to remember is that all these voice-control systems require an internet connection, which can be either Wi-Fi or mobile broadband. Voice recognition technology requires huge amounts of processing power in order to accurately analyse human speech, which could slow down even the fastest smartphone or tablet. To speed things up these digital assistants offload your voice commands to powerful servers on the internet. Your words are then analysed and the appropriate response is downloaded to your device. 

That can cause delays, but we actually found that Siri and its various rivals all responded pretty quickly. Cortana was perhaps the slowest, though - and wasn't helped by its habit of flashing rapidly changing strings on text onto the screen, which create the impression that it's having trouble figuring out what you've just said. And, on our Lumia phone, we also found that Cortana would sometimes pause briefly to update its notebook feature before responding to our commands, which could be annoying at times.

Best voice control tech: Siri vs Cortana vs Google Now vs Amazon Echo - Methods of activation and 'always on' options

Siri, Cortana and OK Google can all be activated in two ways. Pressing and holding the Home button on an iOS device activates Siri, while Cortana and OK Google let you tap a microphone icon on the screen.

However, all three systems also provide an always-on option, which tells your phone or tablet to constantly listen out for a key phrase, such as "Hey, Siri" or "OK Google", which it recognises as the start of a new command. The Amazon Echo will keep listening as long as it's turned on, although there is an option to turn its microphone off if you want to. 

Many people have asked how these always-on option might affect battery life on their mobile devices - and, in fact, most older iOS devices only allow you to use the Hey Siri option when they're connected to a power supply. But when we left our iPhone SE and Windows Lumia 950 running with these options turned on we found that they drained less than 1% of extra power from the battery each hour. In addition, Siri and Cortana both get turned off automatically when your phone battery drops below 20%, so you can probably leave them on all day without worrying too much. 

Best voice control tech: Siri vs Cortana vs Google Now vs Amazon Echo - Controlling the smart home

Of course, the ultimate aim with these voice-recognition systems is a Star Trek future where you control all sorts of devices with your voice commands. Apple's got that future firmly in its sights, and the ability to use Siri to tell the new Apple TV to "find films with Tom Cruise" or "play Game Of Thrones season 3 episode 7" shows the future potential for voice-recognition technology.

Apple's HomeKit allows you to extend Siri's voice controls on to other devices too, such as the Philips Hue lighting systems, or Elgato's Eve thermostat controls. Unfortunately, there aren't many other companies that currently support HomeKit and it's the Amazon Echo that really seems to be making the running here. The Echo allows manufacturers of other devices to create 'skills' that can be used to control their devices, and the Echo already works with a wide range of home-automation devices from companies such as Philips, Nest and Samsung.

Best voice control tech: Siri vs Cortana vs Google Now vs Amazon Echo - Which is the best voice-control tech?

Siri's flexibility and accuracy with colloquial language does make it one of the outstanding personal digital assistants in the mobile arena, but there's no doubt that it's got plenty of competition. And with Microsoft extending across a wider range of devices, and Amazon trying to take a lead in home automation, Apple and Siri will have their work cut out to decide which digital assistant will control the home of the future.

Next page: Our comparison of some of Siri and Cortana's features from 2015, written by Lou Hattersley.