Thinking of buying a new Apple Watch? Wondering if now is the time to make the upgrade from an older model to the shiny new Series 6?

This isn't an easy question, and the answer depends on your needs, and on the specific model you've currently got. In this article we compare the Series 6 with its three most recent predecessors to help you make the right decision.

If you decide to go for it, you can buy the Series 6 direct from Apple, or browse our guide to the best Apple Watch Series 6 deals. Alternatively, read our Apple Watch SE vs Apple Watch 6 comparison and our Apple Watch SE review and Apple Watch 6 review

Apple Watch Series 6 vs Series 3, 4 and 5: Series 5

Apple Watch Series 6 vs Series 5

The new Series 6 stands out visually from the Series 5 thanks to new case colours such as blue and red. Apple hasn't updated the design in more substantial ways, however: the new watch comes in the same sizes as the Series 5 (and Series 4, for that matter), with 40mm and 44mm case options.

Apple's engineers have improved the display, which in always-on mode is 2.5 times brighter than its predecessor. This is an advantage, especially in direct sunshine.

Otherwise, the differences to the Series 5 are quickly counted. The optical oxygen sensor measures oxygen saturation in the blood, and the always-on altimeter is new.

The S6 chip represents a leap forward but, unexpectedly, the wireless chip remains the same as in the Apple Watch Series 5: a W3. In contrast, the Apple Watch Series 6 receives the same ultra-broadband U1 chip as in the latest iPhone 11 Pro.

There are also changes to the battery in the new Apple Watch: not only does the device charge up to 40% faster than the Series 5, it can last up to an hour longer than its predecessor during training. Speaking of chargibg, Apple has also left the power adapter out of the box for the Apple Watch Series 6 and Watch SE. Read: Which plug do I need for my Apple Watch?

Verdict: We'd say the differences between the Series 5 and Series 6 are too small to justify an immediate upgrade. The advantages of the U1 chip, however, will probably only be understood when (or if) Apple's rumoured AirTags tracker hits the market.

If you want to read more read our Apple Watch 5 vs Apple Watch 6 comparison.

Apple Watch Series 6 vs Series 3, 4 and 5: Series 4

Apple Watch Series 6 vs Series 4

When comparing Series 6 and Series 4, the list of differences is significantly longer.

You get a processor two years newer (S6 vs S4), new case colours, the new U1 chip, compass, faster battery charging, longer battery runtimes during training, the always-on altimeter, and the ability to measure blood oxygen.

But the biggest difference is probably noticeable in the display. The display of the Apple Watch Series 6 is not only brighter in direct sunlight, it can also (like that of the Series 5) be set as always-on. This was a long-running criticism from watch purists: when it was idle, the Apple Watch Series 4 and earlier turned off their screens entirely, and sat unappealingly on your wrist like a black block.

The Series 6 is also ahead in terms of capacity: 32GB are built into the new watch, whereas the Series 4 makes do with 16GB. Athletes, in particular, would appreciate more storage: it fits a much larger media library of songs and podcasts, which you can then listen to while training with your AirPods.

Speaking of AirPods, the Series 4 has the has the same Bluetooth 5 modem as the Series 6. But there is still a small difference in connectivity, as the Series 4 does not support international emergency calls.

Verdict: The combination of always-on display, more storage and newer sensors (measuring blood oxygen, for example) makes switching from Series 4 to Series 6 very appealing. Apple is rather stingy when it comes to part-exchange, so consider handing over an "old" LTE watch to the kids and connecting it to your own iPhone via Family Setup.

Apple Watch Series 6 vs Series 3, 4 and 5: Series 3

Apple Watch Series 6 vs Series 3

If you consider that only three years separate the Series 6 and Series 3, it's startling how big a leap forward Apple's smartwatch line has made in that time.

The manufacturer has redesigned the display housing so that the bezels are narrower and the screen area has become significantly larger. The display can now always remain switched on.

In addition to measuring oxygen, the watch can perform an ECG, detect falls and automatically make an emergency call. The battery charges faster and lasts longer. Bluetooth support has moved on from version 4.2 in the Series 3 to 5 in the Series 6.

In terms of the processor, three generations have passed (S3 vs S6), and the latest generation has switched to a 64-bit architecture. And the Apple Watch Series 3 (without LTE) has to make do with 8GB of storage, compared with 32GB as standard on the Series 6.

This and some other hardware factors, such as older speakers and mic, explain why some new features of watchOS 7 are not supported on the Series 3. It can't set a timer for handwashing, and new faces such as Stripes and Memoji aren't supported. The Series 3 also can't be set up as a second watch for your child. 

Verdict: We'd recommend making the upgrade now. In addition to many hardware improvements (always-on display, ECG, blood oxygen measurement, faster charging times), you'll get more out of watchOS 7.

This article originally appeared on Macwelt. Translation by David Price.