Personally, now, Windows and OSX are pretty close. I love Win7, hated f'n Vista. I primarily bought the MBP's b/c I like the aluminum feel, the touchpad and the longer battery life, and the backlit key's which not many were doing when I got the 13". But the Windows laptops have made great strides, you have some incorporating aluminum/metal now, batteries have gotten better and some are fairly close/even with the MBPs in actual use, multi-touch trackpads have gotten better and again extremely close to Apples now.
But I love being able to run OSX and Windows 7 at the same time, there are always things I prefer more in Windows. I.E. I trade, mainly forex, and something about the platforms on OSX I hate. if I'm not around my desktop I'll open Win7 and metatrader.
Desktops though, PC all the way especially for the way I have my media and home theater setup and streaming.