IIRC the razer software that comes with the DeathAdder supports programmability and application profiles. Can the G9 do stuff the DA can't?
You have more buttons on the G9, the mouse wheel alone has 3 buttons. You can switch between a free spinning mouse wheel and a regular one on the G9 with the click of a button. You can change the sensitivity of the mouse in a moment with clicks on the mouse it self. You can switch between several programs you have stored in the mouse (meaning you can switch it to any other computer without having to reprogram it), with clicking buttons on the mouse. You can switch between several grip/shell types "can even buy more". You can change the weight of the mouse. And most importantly, even with all the buttons on the mouse, none of them are actually in the way And when gaming, those are the things I Love about the G9.
I've not actually tried to program my DeathAdder, since I no longer find the time to game much, and the DeathAdder works fine as it is for my usual projects.