I have three gaming mice:
Logitech MX518,
Logitech G5 revision 2 and the
Razer Lachesis.
The Logitech mice are very comfortable if you palm your mouse since it is molded to fit you hand. The MX518 and the G5 are almost the same except the G5 is smoother to move on the pad and has a tilt wheel. The tilt wheel is a bit annoying when you try to push down the middle mouse button, but gives you two additional buttons with tilting left and right.
The Razer mouse is used if you finger your mouse. It is very smooth on the pad and has very very high DPI settings. I tend to palm my mouse which is bad in the Lachesis case because it actually lifts the front of the mouse up slightly causing me not to be able to reliable pin-point accuracy.
I like the Lachesis for TF2 and I use my G5 for Hellgate London and for Frontlines.
So if you have big hands and palm your mouse then the Logitech mice are good. If you are ambidextrous or left handed or finger your mouse, then Razer is better.