Having used all before except for the lasertrac (too expensive), I would say kensington has the best trackballs for me.
I have never, never found any logitech trackball to work well with me.
Two examples:
1)
Marble doesn't roll well. It is long, so you have to use fingertips, but the movements are not smooth and easy like the Kensington Orbit. I often tip the ball out of the cradle - it's not well designed.
I have small hands, and still find the Marble too narrow for me to do the double click (both buttons together).
2)
Wireless Logitech M570 trackball is even more ridiculous. You've got to use it to (un) appreciate it. My thumb gets tired and (inflamed?) after hours on the computer diddling that trackball around.
I would love to hear somebody tell me: I use M570 all day and it works fine with straining my thumb.
Some of us understand the wonderful world of the trackball mouse. I am trying to decide what is best for gaming. I know that every person is different but I am looking for a majority vote. Here are the competitors and let me know if I miss any.
1- Logitech Trackman Marble FX
2- Microsoft Trackball Explorer
3- CST LaserTracX 2545-5XW
4- Logitech Trackman Marble
5- Kensington Slimblade
6- Kensington Expert
I know there are some I am missing and please feel free to mention them but don't forget to give a reason why?