If you want to buy a new Mac, consider buying one with an SSD drive (which stands for Solid State Digital, it has no moving parts) instead of a standard hard drive (which does have moving parts, and is thus slower in retrieving data).
Apple now has customize-to-order options that allow you to get a 256 GB or 512 solid state drive in any model, instead of a mechanical hard drive.
This is good news, at least if you’ve got dollars to spend and don’t have a ton of media to store. Formerly, the only SSD option was 768 GB, and it was only available for the 27″ model (and still is).
Solid state drives are much more expensive per GB than mechanical drives, but they are much faster and less prone to failure. In the 21″ model, Apple ships a pretty slow mechanical drive, so having the SSD alternative makes that model somewhat more appealing if you don’t mind the smaller capacity and higher price.
Interestingly, if you buy an iMac with a “Fusion Drive”, you’ll get both a 128 GB solid state drive and a mechanical drive, though as shipped, you’ll see both drives appear as one. OS X will, unseen to you, shuttle files between the two based on its guesses as to whether you need frequent access to them or not. You can reformat if you want to treat them as two separate drives with nothing happening behind the scenes. (It’s too bad they don’t offer a Fusion Drive option with a larger SSD.)
Anyway, since Macs are becoming more and more specialized and harder to customize on the inside, we’re glad to see a few more choices from Apple.