G502 or the new excellent wireless G602, love mine.
Added bonus is the gigabyte was only a tenner 
Are you saying this as someone that used and liked the MX518? It looks like a very different mouse.

Why is it cheaper?
I changed my MX510 for a Gigabyte M6880. I couldnt get on with any of the current logitech range, they were all uncomfortable for meAdded bonus is the gigabyte was only a tenner
![]()

Probably the rechargeable battery in the G700s making it more expensive. Not that it helps it, the G700s has woeful battery life of 8 hours. I'm still on my first set of batteries in my G602, 4 weeks and counting.
Went from an MX518 to a G602 myself, fantastic mouse :