Mouse for laptop: Normal one or a smaller one?

Anyone like trackballs?

I imagine they're even better with laptops since you don't need any kind of flat surface to use them with.

If anyone's never seen one, here's the one I use (there's a cordless version as well). You move the ball with your thumb instead of moving the mouse itself around.
Logitech TrackMan

Maybe some people are just used to regular mice, but after using one of these for awhile I could never go back.