Feel of the sail is an interesting thing especially in top notch race kit, what makes one guy faster on one brand over another can be is as simple as the fin in the board and its relationship with the sail tested, or the mast track position for one sail relative to another on a given board. The amount of downhaul and so on.....
At the end of the day they all fly, and it's more about picking a sail brand you want to be associated with, that will look after you if you have any problems.
Support and backup that should be a key consideration

My 2 cents