I recently made a switch of mice, and did a lot of testing. The reality is, the MS Sidewinder x8 is my favorite layout, but at 500/s polling, it isn't quite smooth enough for a 120hz setup.
I checked out all the Razers, and none of them had the middle mouse tilt feature, which I like a lot. I tend to not use the middle button click for anything, and use the tilt to the left and right for an added programmable button, though many games I don't need it, in some I feel I do. This eliminated all Razer mice.
I tried the Logitech G400, which is very smooth, but lacks the tilted middle mouse button, and to be honest, I wasn't thrilled about the thumb button layout after using the MS Sidewinder x8.
I tried the Logitech G600, but the software is buggy, and trying to lift the mouse to readjust it's location was problematic with so many buttons, plus, it just was not optimal.
I was going to avoid the wireless G700, but as it turns out, it is the only layout, besides the MS Sidewinder x8, that I liked. However, the battery life is poor, and the charger is not nearly as nice as MS's. However, after using it, the 1000/s polling, definitely made this mouse much smoother than the MS Sidewinder x8, at least with a 120hz setup. While the charger isn't as good, it still feels perfectly fine to play while it is charging.
So, in the end, the Logitech G700 is the best mouse I could find that had a good button layout, tilting middle mouse button, and 1000/s polling.