Mac vs. Vista vs. XP vs. Linux vs. BSD vs anything?

Which is your pick, and five reasons why. Please don't answer, and have one of you reasons be "If everyone used xxx, the world would die" or something like that.
Oh, and BTW this comparison also includes hardware, not just OSes.
No, not homework, me and my friend are in an argument.
Manohar...reasons for Vista over othe
I meant an actual computer. While your answer is clever, it doesn't answer my question.

vista
1. looks nice w/ aero and such
2. compatible with more than macs/linux
3. most common (or other windows-based)
4. runs fast and well if your computer is powerful enough
5. more intuitive than xp