I have a Deathadder and a G5 so I can tell you about that.
Personally I feel that the G5's left and right mouse buttons to be a little more tactile and responsive than the Deathadder's buttons which are a little bit more mushy. They're also a bit more quiet than the G5's buttons. The thumb button on my G5 is a less tactile and responsive than the Deathadder's buttons which require a little more force to actuate and are much more responsive.
Now the middle mouse button and mouse wheel itself, I much prefer the one on the Deathadder because it requires a lot less force to actuate and it isn't a complete pain to hit the middle button. My main problem with the G5's scroll wheel was that it would sometimes hit the side scrolling buttons, the actual scrolling itself is a lot more solid feeling than the Deathadder which seems to randomly scroll on its own sometimes.
The Deathadder is still a nice feeling mouse though, the buttons a lot more solid than my other Razer mouse, a Lachesis, which had ridiculously mushy side buttons and a set of very hard to press mouse buttons on the top.