In our ongoing effort to provide benchmark data to help you choose the right iMac, we now present test results from a 21.5-inch 2.7GHz Core i5 iMac with a 256GB solid-state drive (SSD). You can use these results to compare with the standard-configuration iMacs and two build-to-order (BTO) models with Core i7 processors.

The iMac we ordered adds a 256GB SSD to the standard-configuration £1,249 21.5-inch iMac, which includes a 1TB hard drive. The £480 SSD upgrade brings the total cost of this iMac to £1,729. Apple doesn’t offer SSD options on the entry-level, £999 21.5-inch 2.5GHz Core i5 iMac, so the model we ordered represents the least expensive iMac available with both an SSD and hard drive. If you opt for a 256GB SSD only (no hard drive), this adds £400 to the £1,249 price of the standard configuration.

As we’ve experienced in past lab testing, SSDs are considerably faster than the standard 7200-rpm hard drives. In our overall system performance test suite, Speedmark 6.5, the SSD-equipped iMac outperformed the 21.5-inch 2.7GHz Core i5 iMac with just a 1TB hard drive by nearly 15 percent. The SSD-equipped iMac was 35 percent faster when duplicating files, 8 percent faster when compressing files and 47 percent faster uncompressing files. The SSD-equipped iMac was also 14 percent faster when opening a Word document in Pages, 42 percent faster when importing JPEGs into iPhoto, 9 percent faster at importing and processing photos in Aperture, and 16 percent faster importing a two-minute clip into iMovie.

As you might expect, processor or GPU intensive tasks, like those performed by Handbrake, Cinebench, MathematicaMark, and Call of Duty 4, didn’t reap any benefit from the SSD upgrade.

In overall performance, the SSD-equipped iMac posted higher Speedmark 6.5 scores than the 2011 BTO iMacs with processor upgrades. The SSD-equipped iMac even posted a higher score than the previous fastest iMac, a 2011 BTO 27-inch 3.4GHz Core i7 iMac with a 1TB hard drive.

Comparing the SSD-equipped iMac to the BTO 21.5-inch 2.8GHz Core i7 iMac with a 1TB hard drive, we see that the SSD iMac was about 7 percent faster in our Speedmark tests. Processor test results tell a completely different story, however, with the 2.8GHz Core i7 iMac posting 18 percent faster Handbrake results, 25 percent times Cinebench CPU test results, and a 24 percent higher MathematicaMark score.

When you order an iMac from the Apple Online Store with both an SSD and a hard drive, the SSD is hidden under the optical drive. The cables and bracket used to keep the SSD in place are not included in iMacs purchased without the secondary drive.

As we’ve previously reported, the iMac is not built to be easily user-serviceable and the hard drive replacement process is not recommended for the casual user.

Check back soon for more iMac results, including an “ultimate” iMac configuration with the fastest available processor and SSD. If you have tests you’d like to see us run, let us know in the comments.