Hmmm, I don't like logitech personally, I have had an MX-510 and an MX-700, they both were alright, but without the drivers they were very choppy, I have read that they were cheating with their drivers as well, making the movment smoother with the software somehow, and that the hardware wasn't up to what they said it was. I have never bought anything from razer, but from what I have read the diamondbacks seem very good, at that level of performance, I don't know if having one or the other would make much of a difference. Of course I can think of one thing that the MX-518 will have that the Diamondback won't, on the fly DPI ajustment, I have no idea how this will affect the mouse (I guess it will make the cursor skip a little more as you change the DPI from higher to lower) and if it really is that important. One other thing to consider is the shape of the mice, the MX-510 and 700 were quite comfortable for me, the razer looks a little odd to me, but like I said, I never used it, so I don't know exactly how comfortable it would be.
