I have used both for many years, and while OS X on the MAC is a nice experience, you can have the same experience under Windows 7...

The hardware inside a Mac Pro is really not that different from what is inside a computer running Windows. Custom motherboard just like the big names (Dell, HP, Lenovo) have, but the other parts such as hard drives, memory, and all are the same as in windows based computers.

What you are paying for with Apple is the fact that they have kept things running very stable by having a VERY limited amount of hardware types to run on, while Windows can run on thousands of hardware combinations. Keeping the hardware limited like this ends with a very stable operating system as there is no issues with compatibility between various manufacturer's drivers, which is what caused Windows computers to be unstable at times.

OS X is what it is due to Apple limiting hardware and as a result, insuring stability. If they ever were to open it up, letting anyone install OS X on any hardware, such as what Microsoft allows now, then it would lose the stability it has now, and while still having a nice user experience, would bring in the same issues that Microsoft deals with often.

Microsoft could release their own PCs, running on their own hardware, charging like Apple does, but they chose to release a product that works on any mainstream hardware out there, giving it the large flexibility it has now...

So it all boils down to one question really, how much do you prefer to spend on your PC? (Windows and OS X systems are both PCs, Personal Computers)