Very subjective I know, but..
my bestsest friend, not wearing his helmet, was involved in an ugly aeroplane accident - 5 weeks in a coma and fractured his spine
Guy in the back, wearing his helmet and closer to the panel, fractured his spine in the same place (L5 &L6) and pulled himself out of the crash
I always wear a helmet, Pitts, Cub or Arrow!
Stik