I used the MX518 and then a Naga before my current white logitech 600. Love it. Had it two years ish.

I really hated the razr software. I have normal sized (I assume) female hands but I have no issue using the mouse. If you want to work on training yourself set all the keys to numpad keys and then use a 10 key training game a few times, I don't have any problems learning keys I do often and I use the side keys a lot for things other than gaming (cut paste text block inserts). Great weight, great drag, great precision, no issues with wear and tear after two years even on the mouse wheel.

Pros:
Ergonomics!
Software!
Durability!
Number of keys!

Criticisms: I would really prefer a single profile possibility for game modes so that I never have to cycle to the right one. For most games I just want one profile and I don't want it to ever be doing anything else when I click the keys. Keeping all three profiles set is too tedious, so I end up having one "good" color and two blank profiles that are red so I know the mouse needs to have the profile toggled.

White mouse looks dirty.

I often forget the extra ring finger key. The only time in my life I've ever used it for anything was recently when I was... playing cookie clicker and I wanted to spam the left mouse click. It doesn't trigger accidentally but it has never felt intuitive to use it.