The 12 side buttons on the Razer Naga Chroma have mechanical switches inside. Mechanical switches have a great tactile and audible feedback while also having great longevity. The buttons themselves are also angled which makes it easier to find the correct button to use.
There is a button below ones pinky on the G600, which separates itself from other MMO mice. Basically it is just another programmable button that is easy to reach just in case one wants to use it.
Unlike the Razer software which is basically always online DRM, Logitech provides software that stays out of the way, does not require a constant internet connection and uses less resources than the aforementioned competitor.
Normally a mouses scroll wheel will click in the center and turn but the G600 also has a left and right click to the scroll wheel as well. This just gives extra functionality that can be programmed to an easily reached area.
Often mice in this price range ($80) offer ways to customize the ergonomics. Sadly there is nothing like that with the G600 making for an uncomfortable experience for extended play times.