the change is FPS depends on the program and your video card really..
if you are using a Nvidia graphics card, you will not see any loss in FPS
if you are playing a game through Wine, you will see a loss in FPS
if you are playing a game which has been ported over to linux and you play it from an X windows (command from console is 'xinit') you will see substantial increase in FPS
if you just plan to play games, stay on Windows.