Personally, although I have a G5 v2, I am still using my old MX 510 (you can still get the MX 518 for a pretty decent price, which is the same thing but with updated design). You won't make a mistake with any Logitech or Razer gaming mouse, just watch for the number of buttons or other features you may need or want. In my personal experience, both are as responsive, but Razer has better software and drivers but also worse secondary buttons. I think Logitech also has a bit of an edge in the build quality department. Anyway, it's a matter of personal taste, but I would look into those two brands if I were you.