In the past, the OS is what made a Mac run 'faster' than a Windows PC. Now that Macs are all Intel-based, it's actually silly to pay Apple's ridiculous markups on what is a middle of the road PC from a hardware standpoint. For the money you pay for one of the Mac Pro's, you could get far more computing power buying your own components.
The trick at that point is getting OSX to run on that hardware :D If anyone is curious, check Project OSx86 or Hackintosh.org. The developments in the age old Mac v. PC debate have taken a quite unexpected turn ever since Apple went to Intel. Quite frankly, not much of an argument any longer. In the end it's better for the (enterprising) consumer.
