I have been using a G5 for years now and am quite happy with it.
Doesn't mean it will fit the best in your hand though...
The best thing you could do is take a trip to your local big box store or computer shop and lay a hand on the demo model.
I was checking amazon or some other website (don't remember which one exactly), there it said G5 is out of production. G500 is the newer version of the G5 and G9x of the G9!
I would say stick to Razer.
What's your budget for the mouse?
I'm sorry for not including that my previous mouse was a LOGITECH G5 (v.1). I have used it for years but it has taken quite the beating, so I'm looking for something else. The g5 was indeed a GREAT MOUSE, so im hoping to get either the:
DeathAdder, (More of a Palm Grip mouse, but very ergonomic sized.
Ikari Laser, (Not 2 sure about this, heard its for gamers w/ smaller hands)
G5 v.2 (Same as b4)
G500 (Side buttons are small i heard)
XAI (seems a very complex mouse to use)