Steelseries Xai is a fantastic mouse.
I've tried many, many mice over the years (including all on your list) and to me the Xai is by far the best. Its really in a class of its own.
It is very comfortable, tracks impeccably, very smooth glide (esp. on the SS 9HD pad) and has perfect button placement and action.
I feel like a headshot machine with this mouse, far more accurate that with any other mouse I've ever owned, and I've owned a LOT.
Since you're still shopping, be sure to give it a try.