OSX is probably the better OS but has nowhere near the level of software & hardware support. I honestly cannot think of any reason why someone would choose OSX over XP.. Except maybe hatred for Microsoft but if people hate Microsoft, I don't see why they wouldn't hate Apple.
I have a PC with XP pro at home and play a lot of new games, no problem.
However, I fix PCs and networks during the day, and use a powerbook running OSX, great for plugging in to loads of different networks as it is so easy to configure, and you don't have to worry about viruses.