OK, first, someone mentioned OS war? No such thing. Macs hold a huge 2% to 3% of the computer market. But it's stable there, have been for a few years, no increase, no decrease.
The fact is this: if you work in the graphics industry, get a Mac, if you work in anything else, get a PC.
And BTW: Macs ARE INDEED better for graphics. Do the test yourself. And even do it with a lesser processor for the Mac. Say a 1 Ghz proc for the Mac and a 2.2 Ghz for the PC. Same amount of memory (make that 1 Gig of RAM). Open Photoshop. Open a large image (say a 1 Gig TIF file). Now do some manipulations. Crops, resize, rotate. Apply some filters (try a radial blur on that image, you'll have fun... you'll probably have time to go get a coffee - at the coffee shop at the corner - and come back before your PC is done processing it, if it doesn't crash in te meantime. That's a fact, tested and true. Try it yourself, you'll see.
I'm not sure though if it's because the machine itself is better. I doubt it, cause where everything else but graphics is concerned, I hate Macs, I find them slower and and clumsiers than PC's. I think that maybe the reasson for this increased performance for grahics apps on the Pcs is that the software manufacturer make them first for the Mac and then afterwards make a Windows version. believe the software is probably optimized to work better and faster on a Mac.
A friend of mine at work just bough the new G5. Guess how long it took him to resize a 30 GIG document? 5 seconds. OK, he has 4 Gigs of RAM in there, but still...
Anyway, the bottom line is as I first said: If you work in a company that makes graphics, you'll need a Mac, otherwise just get a PC.