That's old Mac vs. new Mac, but there's a lot of momentum in the gaming world towards the PC due to the Mac's previous horrible performance.
Things like 3D rendering are MUCH faster in Macs these days due to the new IBM PPC970 chip in them, the son of the POWER4 server chip and a cousin to the chips used in IBM's blade servers and supercomputers. This is why Renderman and Maya are out for OS X now, why XServes are getting popular for supercomputing (the #7 Mac system is cheaper than any other on the Top 10, possibly Top 20), and why they used 600 G5 Macs to do the cleanup work for the new Star Wars DVD release. They are far more worth their price than they were three years ago.
If you do image or video rendering, you might be interested in this bit. The next version of OS X, Tiger, will allow applications to easily offload much of the image processing work to the graphics card. Can you imagine the increase in speed when your GeForce 6800 Ultra is doing your image processing with it's 256-bit, 35.2 GB/sec graphics core? And that ability won't cost you anything extra above Macs with the current OS, unless you're upgrading.
What ever works for you, it's the arrogance of MAC users that ticks me off. High prices don't necessarily mean better. It's what you are used to. I mean for $150 less you can get an MP3 player with more storage and the sound will depend on your speakers. If you want to support that Marxist, Al Gore loving Steve Jobs, be my guest.