about gaming mice, what I think should be considered are sensor, shape and weight.
- sensor: Rival 600 has Depth Perception sensor, well... even if you don't lift your mouse that much, this is a nice addition.
- shape: depends on user, though Rival 600 has a nice shape.
- weight: Rival 600 has good weight and it also can be customized.
a while ago I use Logitech G502, I keep it mainly for its buttons. It's heavy, I must use a hard-mousepad (Logitech G440) to offset that, but my hand still got tired in long session of playing.
I have switched to use Trackball, one with many buttons (Elecom HUGE), for everyday use and when I want to play game, I use Logitech G403.