I'd say go with Office. I used Word for all of my notes during my biology undergrad, and I've been messing around with the Pages trial today and just can't seem to get the layout I prefer. I was hoping to switch over to iWork as I start grad school, but I don't think that's going to happen. Pages doesn't do lists as well as Word, has no (free-draw pen (that I can find) to scribble down little diagrams (did this often in Word) and just altogether feels more geared toward self-publishing via personal websites and blogs than it does for true word-processing (read: it feels pretty, not professional). Maybe I just need to get used to the styles format that Pages is based on, but it doesn't seem, at the very least, like it would make my note-taking/paper writing any easier/faster/better than word, and I'm not THAT much of an apple fanatic to spend extra time trying to get what I want out of Pages just so I can use an apple app. I'll put some more time into iWork to get a better idea, but I'm pretty sure I'll stick with Office once classes start back up.
Oh, and it saves files in a .pages file format. I was under the impression you could just choose the default format to save to, so I could use .doc, but you can't (at least to my limited knowledge). Saving just creates the .pages file, you have to go to "export file" and choose ".doc" in order to get a .doc that you can share (same for pdf, but I honestly never had need to create pdf's in my undergrad career, it was all doc's). It's a minor thing, but an extra unnecessary step. And you will almost undoubtedly have to have most of your files in .doc format for file sharing to your pc using classmates and professors, so save yourself the trouble and use Word. I'm sure your school will have at least some sort of discount on the software.