TrackBall all the way, I have been using one since the Original Logitech TrackMan (PS/2) and recently Upgraded to the newer Trackman Wheel that's grey, They are great mice. Since i have more than one (sometimes more than two) computers on my desk, it's great for space since i don't have to move it around, and it's much more comfortable.

On the down side, They are rather expensive, I paid about 40 USD for mine, which IMO is a little more than the run of the mill mice out there that are just as good.

Blake.