Ok... Flame shield up.
Windows
Pros:
Good for gaming
XP was a pretty good Version.
Cons:
Sometimes have very bad technical errors.
Very prone to viruses
Mac
Pros:
Easier to navigate and use for people who do not know a lot about computers.
Very hard to get viruses (it's not impossible though, so keep quiet windows fanboys :I)
Cons:
Not designed for gaming
No right click for the mouse that comes with it. So that's means you buy a new one that has a right click.
Ok, that's just all IMO.