Windows > Mac for games. Even though World of Warcraft is supported on Mac. It was a hell to set the mouse sensitivity to my preference. The Mac OS X's default sensitivity + acceleration is not fast enough. There is a solution though, by using either SteerMouse or USB Overdrive but you have to sacrifice your Logitech Control Centre for your Logitech keyboard if you've got one.

So in the end, I stick to Windows for gaming and Mac for serious work.