the mac mini, especially with boot camp out now, makes the most sense since it's cheap and it will suffice for nearly any major
of course if you are a design major, get the imac or even professional powermac since you will want the power and choice of screen size...or even crt if you are doing video editing or game design
a mbp sounds nice but remember they are far easier to break (by dropping or spilling something on it) and people could steal it from anywhere you work...when you have a computer in a room, all you have to do is secure the room
when you are out using your laptop, you are always taking a chance unless you carry it everywhere with you like i did with my ibook...and i still have my ibook...but it was a pain always worrying about someone stealing it if i brought it out
some people get a laptop for their room, due to space, and rarely bring it out and that is also a good option...especially if you buy a kensington security lock for it...not perfect but if someone was determined enough to cut the cord with a heavy duty wire cutter, they would also find no problem in planning to break into a room and steal a power mac
and also desktops just last longer since they are not always being lugged around and having their delicate parts (modem, ethernet port, keyboard, lcd) always fooled with and touched/plugged/unplugged