Less than a year after the chassis overhaul that gave the iMac its new slimline bodywork, Apple's innovative desktop computer enjoys another revision. This time, it's a minor refresh, bringing Haswell processors, better GPUs and faster WiFi, but retaining the form factor of the previous generation. It's an unsurprising move.

Last year's update had already radically redesigned the all-in-one Mac, dropping the optical drive in favour of a new slimline design with better speakers, a revamped and less reflective screen construction, USB 3.0 ports and a second Thunderbolt port. The upgrades for this year's model are all internal. If you were hoping for a Retina display, you'll be disappointed.

Apple 21-inch iMac

Naturally, the iMac isn't the only slimline all-in-one computer out there. Lenovo's IdeaCentre B540p starts at around $720. It has a 23-inch touchscreen panel and 3D capabilities. The Acer Aspire 5600U costs about $730, but it's a great family media center, and the Asus Transformer AiO P1801 with a starting price of $1,000 is a hybrid tablet and desktop with two separate processors, one running Windows 8 and one running Android 4.1 Jelly Bean. For $629, you could buy a Lenovo ThinkCentre M92p Tiny. It's not an all-in-one, but the PC is extremely small.

If you prefer to stick with a Mac, Apple's other desktop option is the Mac mini. This small form factor machine is the cheapest way to own a Mac, though it doesn't come supplied with a display, a keyboard or a mouse. The top-of-the-range Mac Pro isn't currently on sale in Europe and is about to be overhauled with a new release, so now is not the best time to invest in one.

Apple 21-inch iMac

As the new iMacs share the previous generation's form factor, they also suffer from the same limitations. As mentioned before, there's no optical drive, so if you want to use DVDs and CDs, you need an external model such as Apple's own USB Super Drive.

Upgradeability is also a problem. On these 21.5-inch models reviewed here, you can't add memory yourself, though a configuration option is available if you order from the Apple Online Store. Also, as the screen is glued in place instead of held by magnets, it's more difficult for even specialists to access the internal components.