For gaming, PC's smoke Macs. The only benchmark you can find in most any comparison is Photoshop, which is optimized for a Mac. Comparing Photoshop on Macs and PCs seems kind of like comparing an old game that was optimized for Glide on a 3DFX card to the same game on a card running D3D or Open Gl. Of course the Glide will beat the other because that's what the game (like Unreal 1) was optimized for.
I did a google search for macs vs. pcs and came up with several test, which naturally uses Photoshop as their main benchmark. The Mac sites really made a big deal out of Photoshop, and pretty much glossed over the fact that in games the Mac got beaten much worse than the PC did in Photoshop.
I also found one comparison that said while Macs could win synthetic cpu benchmarks, in real-world performance, PC's were faster.
They also whined about how the video cards and drivers for PC's were better, etc....but that's not the PC's fault. You have to use what's available, and the fact of the matter is that there is far, far more hardware and software available for PC's than there is for Mac.
Plus, the fastest PC now is more than likely faster than the fastest MAC, and you can buy or build that PC for much, much cheaper than the Mac, and your peripheral options are far greater.
I personally prefer PC's, but I don't say Macs suck.....I just don't see why anyone would want one over a PC except for the novelty.