Ok, I think I'm actually going to go for a iMac.
There's a few reasons for this:
Honestly, I don't think I need a portable computer, at least in the foreseeable future. The classes I take don't require me to have a laptop at school or in class. And honestly, I wanted a solid computer to use at home. So, for price to performance ratio, I think the iMac is a better deal, no?
And if I did want to do occasional gaming, wouldn't iMac perform better?
Now it comes down to if I want to buy the 21 inch and that will suit my needs or if I need to spend almost 2000 dollars on the 27 inch model. What model and configuration would I need? (obviously, the Haswell update is gonna throw all this off.)
I own a 2011 27" imac and find the larger screen somewhat of a mixed blessing.
First, font sizes don't scale properly in OSX. You will find that with the 2560x1440 resolution, fonts will appear comically small (and there isn't any way to increase them). I had eye strain in the beginning, that eventually took 2-3 weeks to get used to. These are things that become apparent only after days of extended usage, and isn't something you can get a feel of at the Apple Store.
2nd, the graphics card for the base model isn't really sufficient to power modern games at full res. When gaming in bootcamp for example, I typically run games like darksiders2 at 1920x1080 windowed mode, because it looks horrible in full-window mode, or lags at full-res. I think the high-end model might be out of your budget. It will support popular Blizzard titles like Diablo3 and Starcraft2 at decent resolution though.
3rd, I find that the screen is excellent for working on full-screen excel spreadsheets or viewing word documents 2-3 pages at a time. However, when surfing the web, I typically have to stretch Safari to about 2/3 of the screen's length to be able to view the contents comfortably, which doesn't really leave room for another app open (resulting in a lot of wasted space). Chrome scales better in this regard, but I like to keep to Safari across all my Apple devices.
I still don't regret my choice, but given the nature of my needs, I sometimes wonder if I might have been better off with a 21" imac + 21.5" display, a mac-mini with two 23" monitors (I just don't have the time to game these days), or even a thunderbolt display (but I share my imac with my dad, and sexy as the idea sounds, the total cost at the time was outside of my budget).
If you plan to game, I recommend the base 21" imac (I find it the safest choice). If you can live without gaming, a mac mini would work just as well.