I have used 7 Deathadder in the past and it feels really comfortable, for an extended period of time I thought I would never switch to another mouse until one day I realize that my 7th Deathadder in 4 years have broken and I have to take my MX518 out from my drawer (again) as a backup.
Then i thought, this mx518 lasted like decades, why not give some other Logitech products a try, bought the G502 at June, no complain so far and it looks a lot sturdy then the Deathadders I had, especially since this is the first mouse I have in 3 years that lasted more than 4 months.
The higher DPI of the proteus core is really handy while working on multi monitor.
Anyway, since you mentioned CS:GO, I think the "Sniper button" would be really handy for you.