Blue is better
This mouse is a great choice if you plan to mouse on your leg, carpet, bedspread, and other unlikely surfaces. 95% ambidextrous, the position of the thumb button shouldnt be a deal-breaker for left-handers.
As advertised, the mouse tracks better on strange surfaces than an ordinary mouse; You can see the blue LED on the bottom, and blue has a shorter wavelength than red, so the sensor gets a better sampling of the mousing surface.
The scroll wheel has no tactile feedback, though its very smooth; This is a matter of taste, but I prefer clicking; Left-handers could be annoyed at the placement of the thumb button; The mouse is otherwise symmetrical they might have just put aux buttons on both sides.