You can't upgrade the 21.5-inch iMac after you buy it, so consider paying an extra $200 at the outset for a memory upgrade to 16GB. The 21.5-inch iMac also offers a 1TB Fusion Drive upgrade or a flash storage upgrade. The $1299 and $1499 iMacs offer a 3.1GHz quad-core Core i7 processor upgrade for $200. The $1099 and $1299 models don't have a processor upgrade.
The 27-inch $1799 iMac carries a 3.2GHz quad-core Core i5 processor and a discrete Nvidia GeForce GT 755M graphics processor with 1GB of video memory. The hard drives in the 27-inch iMac is a 7200-rpm drive, with Fusion Drive or flash storage upgrades available.
You can upgrade the RAM on the 27-inch iMac easily. The machine has four RAM slots, accessible through the back. Apple installs the standard 8GB as a pair of 4GB memory modules, so you can add more RAM after you buy the system. Or if you prefer, you can upgrade the RAM at the point of purchase to 16GB ($200) or 32GB ($600).
The iMac comes with Apple's Wireless Keyboard and Magic Mouse. If you order online from the Apple Store, however, you can switch the keyboard to a wired version with a numeric keypad, and switch the mouse to an Apple Mouse or a Magic Trackpad, for no extra fee. You can opt to get both a Magic Mouse and a Magic Trackpad for $69 extra.
The iMac does not have an optical drive. If you want to read or burn CDs and DVDs, you need to buy an external USB optical drive.
How do I connect stuff? Wi-Fi and Bluetooth are built-in. All iMacs have four USB 3.0 ports, two Thunderbolt ports (not Thunderbolt 2), a gigabit ethernet port, and an SDXC card slot.
If you want to connect a FireWire device, you'll need to use a Thunderbolt-to-FireWire Adapter. USB 2.0 devices can connect to the iMac's USB 3.0 ports.
How fast is it? The iMacs are among Apple's fastest computers, but their hard drives are a performance bottleneck. If you can upgrade to a Fusion Drive or to flash storage, you'll gain a significant performance boost. The $1299 iMac's graphics performance is good enough for games, but the discrete graphics in the other iMacs are much faster.
The $1099 iMac has an attractive price, but you make huge sacrifices in performance. Our benchmarks show a significant difference between the $1099 and $1299 models. Even the 11-inch MacBook Air with 256GB of flash storage is faster than the $1099 iMac.
Macworld's buying advice: For new Mac owners, the $1299 iMac is a good alternative to the Mac mini, providing a nice performance increase. If performance is your top priority, consider a Fusion Drive upgrade, or even a faster-processor option. On a 21.5-inch iMac, the 8GB of RAM should be fine; but buying the RAM upgrade at the point of purchase could help you avoid some hassle in the future. The 27-inch iMac is ideal for demanding users who need as much speed as they can get.
Sign up for CIO Asia eNewsletters.