That's really old school thinking. But a sizeable portion of the new gaming mice that seem to be getting traction based on their looks (RAT, I'm especially looking at you) have crappy sensors, poor balance and badly weighted switches.
But personally I think the fit is the most important thing. I don't mind the G9x as a mouse in functional terms, but it gives me long-term finger joint ache. And this is something you can only decide. The adjustable mice are for the most part smoke and mirrors, it's important to get a mouse with a basic shape that suits you.
The G700's not a bad default to start off with IMO, and it's about as universally unoffensive a shape as I've come across in terms of fit.