Is there a store where you could try the mice out? That is really the best way to find the most optimal mouse for you.
I wouldn't buy an MMO mouse unless MMOs are the only games you play/you are a professional or a competitive player in MMOs, or if you do a lot of work that requires key shortcuts. Even then I'd just probably take a normal mouse and use my keyboard for the shortcuts. MMO mice tend to give less support for your grip than normal mice do so you'll do much better in FPS and similar games with a regular mouse.
If you like the G502, wait for the new revision. Some people have received Proteus Spectrum labeled G502s as warranty replacements from Logitech so it could be that it will be in stores before Christmas. I am quite sure the Spectrum version has RGB-lighting. G502 has the best available sensor to date.
