I'm not, I use both Windows and Mac almost equally (on different computers, mind you). Though I've had my Macbook Pro for about 2 years.
Performance for 90% the time will be the same, however 3D graphics-intensive things (ie. 3D games) will usually be better (to varying degrees) on the Windows side, due to the better graphics drivers and the ability for games to run in DIrectX. Mac doesn't have DirectX, so games are often ported to OpenGL/CL which comes with performance overheads.
Browsing should be the same, provided you use a cross-platform browser, like Chrome, Opera or Firefox. That said, Firefox for Windows has hardware acceleration, so complex pages should scroll smoother.