Macs are prettier. And their operating system Mac OS X is way better than Windows XP, even Vista. It comes with everything you could possibly want. Just plug in a camera and your photos will be transfered to your computer without installing any third-party software. Watch DVDs and videos downloaded on iTunes with the included remote control. Video-chat with your friends using the bulit-in webcam and included, pre-installed software.
Have you ever tried to install a webcam on a PC? I've tried to do it on my mom's PC, and it's absolutely hell. You have to install the camera's software, look for an empty USB port (or plug in a bulky USB hub if there aren't any more left), download and install AIM, and then look for a way to make the camera interact correctly with it. (I'm still having trouble with the camera's crappy microphone.) On my Mac, it was as simple as signing up for AIM. The webcam and microphone are already built-in. I didn't even have to download and install AIM's software because Macs already come with a program called iChat that's designed to work with AIM accounts and, more importantly, work seamlessly with the webcam.
The only thing Mac OS X isn't good for is hacking. But that's not a problems because now all new Macs can run both OS X and Windows (XP or Vista).
I have a Mac with both operating systems, and I use Windows XP for ROM Hacking and OS X for everything else.