I have the G9 and have used it for a few years now. I like the larger size and ability to add weight to it. It’s a true FPS mouse.
As for the Razer mice, I have owned the Naga but it is really built for MMO play. I have also tried some of the other Razer mice geared toward FPS but they have all been much smaller and lighter than the Logitech mice.
I would say you are in for an adjustment period if you go with the Razer since all of their models are built so different than Logitech.
I still have my PC setup but I just can’t find much time at all to play. What are you guys playing? It seems that activity has been quite low lately. Is that because there is not a single multiplayer game that interests everyone? I have seen some reviews on the Aftermath expansion pack for BF3 and it seems to be well received.