I'd buy the mamba myself if I could afford it. Damn sexy imo. But yeah, I love my cheapo Razer Salmosa it's lasted me years now. Razer may be expensive, but they sure make stellar products.
I'm thinking of getting the Steelseries Xai myself. I'm a lefty and this mouse seems like it will be suited for left hand use. I also quite like the basic look of the mouse. If I had money to burn, I'd get the Mamba.
There's no such thing as the "best" mouse. It all comes down to personal preference. I'd check out some reviews from consumers on what their grip is with the mouse and what it feels like.