I got the M6900 recently when to replace an old MX518 (the old model of the G400). I thought it was going to be a temporary thing but found that it feels good (for right handed) works pretty good and cheap too. The laser M6980 is not a good idea since there are very few decent laser mice which are good for gaming. There is no angle snapping (or too little if it is present to be annoying) with the M6900.
Try out the M6900 at lowyat, Sri has the display models. And use 800dpi for gaming, 1600dpi for windows(or gaming if you prefer high dpi), anything higher will get too much jitter.

Cheapo plastic buttons.
Its not a small mouse and the size is similar to the g400. The dimensions of both mice are on their websites. You should try out the display model.