Wow and I thought slashdot was bad...
Seriously buy the kind of computer you like. If you're familiar with Windows, scared of switching, or have some application that won't work on Macs, stay with a PC. Most of the major stuff works (well, except games), but the little niche apps are the ones to worry about. You can always run Windows on the new Intel Macs, but you technically have to buy a copy to use it.
I have to agree with the sentiment that Macs are more secure, however. Until IE7 and Vistaa come out, Macs have the advantage for a couple of reasons. One, IE6 is notoriously bad about security holes due to ActiveX crap. You can get around this by using Firefox of course. Two, Macs are based on Unix (BSD specifically), so everything is run in user mode by default. Windows XP runs in administrator mode by default, meaning any application can basically do whatever it wants. This can be catastrophic if a malicious app somehow gets onto your system.
Both have good and bad things about them - buy what is best for you.
A few points though:
-You can run media player files with Flip4Mac
-You don't have to be an idiot to make Windows crash, I'm sorry. It's much more rare now, but definitely happens