I have a Mac, had a PC a few years ago and would never go back - it crashed on me while I was finishing up a final psych paper. Friends of mine at university who have PC laptops complain about them constantly, especially the battery life and the viruses. I've had neither problem with my MacBook. I know girls in the nursing dept who have to bring their power cords everywhere for their PC laptops because the battery dies within 5 mins of being unplugged, which kind of defeats the purpose of a laptop if you ask me.
Plus on any Mac computer you can run the windows operating system if you really want to/need to. Although the Mac laptops are more pricey, they last longer and (in my opinion, I know many will disagree!) are a better product. Plus with a Mac although you're paying more, you get a lot of high quality software included that is already installed on the computer. They also have a really great warranty program, I had one key that was sticking down because I got some juice on it and they replaced the entire keyboard for free. BONUS - If you purchase your computer from a Mac store/online in August or September and can prove that you're a student, they include a free iPod touch (or at least they've offered that the last few years).