I could tell a big difference from 760s to 790 give or take.750-760mm seems to be as what most people are running and that is on a very fast and wide open track so they must purely be going that length for feel and not risk of hitting tree's as there weren't many at that track.
O and regarding Greg Minaar having his bars at 758mm. Do you really think he would be able to tell the difference of them over 760's if his mechanic just left them at that. I realise he is at the top of his sport but really?