There cannot be any definite answer to this question. And one shoe does not fit all anyway. I might tell you that I love this particular operating system and that it is THE BESTEST OS EVER and you might use it on my insistence. Next thing I know, you are swearing at me for recommending you such a crap system.
So the best solution is to try them out yourself. Install Vista (if your PC supports it) or see demos of it on YouTube, use some Linux distros (Ubuntu seems to be the best one at present) and go to an Apple Authorised Reseller and try out a Mac. If you are not planning to spend anything on hardware, don't bother with the first and last option. Windows XP is best for you then, unless you do not mind the initial hurdles of switiching to Linux. Once you make the switch from Windows to any other operating system, however, it is pretty difficult to go back to Windows.
So if Windows is a primary requirement for some reason or the other, just curse God for giving you such a rotten luck and stick to it. Of course, you might also like Windows, which is good for you. So stick to it anyway. If you have the hardware to run Vista, I would recommend you to upgrade. It is better than XP. Do not use the Home Basic version and do not upgrade to it if your computer is incapable of supporting the Aero interface. To quote Digit, "Vista without Aero is... err... XP!"