For gaming, I'd have to say the ball mouse is better.
I'm a hardcore FPS player and have a Logitech USB Mouseman with Wheel. Initially, I was bent on replacing it and going with optical. I waited for the second and third generation opticals to come out, so that the kinks were worked out and I could possibly game with it. So, when the dual optical hit the shelves, I immediately picked it up.
My first impression was: my USB Mouseman will be collecting dust. The dual optical could do the "flick" necessary in FPS games, so I was ultra impressed. Then, after playing for a bit, I found that there are certain movements that just didn't come out as well, compared to my ball mouse.
I went through changing the surface of the mousepad for the optical, along with getting the mouse "skatez" and it still doesn't solve the movement issues I am having. In the end, I have both on my computer: dual for desktop, ball mouse and everglide surface for games. This really pisses me off that I can't use the optical for my FPS games, but if I wanted to stay at the top with my score, it was the only option I had.
vash