I must say I agree w/ the previous post, this is an endless debate, but as an Apple computer owner I thought I would present you with the other side of the story.
I have a Powerbook G4 15''(as in before intel macs were introduced) meaning I can't run Snow Leopard when it comes out(the next OS from Apple) and I have never once had a problem with having a mac and compatibility. I do not use AutoCAD in my studies, and yes, that would require windows, but worst comes to worst you can install windows on your own computer. There are plenty of library and other computer clusters on campus that all have AutoCAD on them too.
In the end its up to you, but I will say this. Apple hardware can run OS X and windows, but Dell can only run windows.
Hope you enjoy your time at tech!