I LOVE macs. I have an iBook G4, and I cannot wait until I can save money and get my hands on a MacBook. First of all, aesthetically, Mac beats any other computer out there (well, maybe some competition with Sony, but not much). Second, since you want a laptop, you would want one that has lots of battery power when unplugged. My computer is about 2 years old, and I can still use it unplugged for three hours straight. The batteries of other PCs go downhill fast! Third, I have found that macs tend to slow down less over time. With Windows, after you have owned the computer for a year or so, it takes a long time to open the computer and to open programs. With macs, even if your computer is 2 years old, the computer processes what you want to do very fast.
I agree that you need some time to get used to a Mac if you've owned other computers all your life, but once you get used to your Mac, you will love it. I know I did.
Oh, and if you have any problems with your mac, you just show up at a macstore, sign in, and a mac expert tries to fix your problem for free. My mac's dvd player wasn't working, I took it to a mac store, and an expert guy worked on it for 40 minutes. Didn't pay a dime. It works very well now.
Sorry for the long message, but one more thing. If you are going to start college soon, most computer companies give education discounts. I know mac gives 10% off, I don't know about dell, but it's worth looking into.

Good luck picking your next computer.