The look of the OS is trivial, especially when Apple choses to favour a brushed steel look on it's apps pioneered by Atari with their 2600. Who cares though? Yeah, XP is hideous, but you can chose a classic look, if you want.
I have my qualms with both OSX and 9 and Windows XP, but in the end, I find that I can function well with both.
If I had to chose, I'd stick with OSX, only because it has been much more stable in my (limited) experiences.
Rade