Get a computer that supports 64bit, you will regret not getting a 64 bit computer if you want to use the newer version of After Effects. Also 64 for bit programs can use more memory, in a good way, if you are using a 32 bit computer and the program you are running use more then 2gb of ram then it will crash. Honestly, both Mac and Windows 7 both work fine so get what works for you. Macs do have a better color management but it is negligible in my opinion. The hotkeys are barely different, if you have half a brain. Working between the two(as long as you save as the standard files for both windows and mac which are is most files). You will have more difficulty working with older and newer versions of Adobe products then between the two OS.
I always liked working on my Windows 7 machine and printing off Mac.
Go for a macbook pro. I know people say PCs are just fine, but at a lot of art schools, they'll either laugh at you if you have one, or tell you to buy a different computer. Some places are so adamant about what kind of computer you have that they actually buy it FOR you.
Question! Which art school are you going to? I've done a ton of research on a lot of programs, so I might be able to tell you exactly what you're gonna need.
I dont think Savannah makes you have a laptop. I totally understand the need for one though. I'm going to Memphis College of Art. They had a similar policy on them. I got a macbook pro just in case. Using public computers just seems like a pain in the ass, you know? Considering you're going into animation, you need a lot of RAM.
I personally had a ton of success looking for a laptop on craigslist. I got my macbook pro for $800, and it works great. If you go that route, make sure nothing is fishy though. Make sure everything works, like the cd drive,usb drives, and run a system diagnostics check.
If you go the apple route, you might want to upgrade that RAM, and possibly hard drive space. Video takes up a LOT of space.
Something with alot of Ram. more Ram the better, though id your doing 2D, you might not need anything too specy. It would be good to invest now, however, so you dont have to consistently upgrade.
personally i hate macs. They are over rated, their parts are more expensive if you do want to upgrade and though they are faster, they do manage stuff slightly better, not worth the hastle. my pc is perfectly fine.
If you want to build it yourself, i advise using scan, its an online store that has insurance, so if you put in the motherboard and it explodes, its okay, because you can return it and get a new'n. There are alot of computers though, try to learn parts and when you go to a store, make sure you arent going to be taken as a mug. Write down all the specs of the pc,. find the best you can (: