I would have been happy with just a PC... (I had a computer, but it was an Apple IIE; yeah, I'm old...)
You have to consider that there is a likely chance that your computer will become "the community computer" - all of your roommates and neighbors in the dorms will want to use your computer, with or without your permission. Also with 5 roommates in the dorms, chances are pretty good that people will be able to walk in and out at will, so there is the chance of theft of a laptop. But, with a laptop, you can lock it up when you aren't using it, so that has it's advantages also.
If you have visions of sitting in class and taking notes on a laptop, it's one of those things that sounds good in theory but sucks in real-life.
Just my preference, with all other things aside, I much prefer to write long papers on a desktop. Laptops are great for writing short memos or checking e-mail on the road, but for writing long term papers, I hate that little keyboard and mousepad. If you do go the laptop route, I suggest an external keyboard/mouse and a decent sized monitor.
But, whatever you take to school, expect it to be shared...