it all depends on set up mate.

avgas is used when people up the compression ratio by lowering the head volume or when the std set up of the bike was for leaded fuel. my rs is a 98 unleaded bike but is now set to runs avgas, more ultimate performance could be achieved with unleaded race fuel but avgas is used at it helps with jetting and preserving the engine.

the 50/50 mix people use is normally for safety, lets say if someone had lowered there head volume but not all the way down to a avgas volume or was concearned there set up did induce detonation.

i used BP ultimate in all my roadbikes and used it on the track for trackdays. its perfect for std engines as thats what there set up / jetted for.