IMO there is only one universal position for the mouthpiece - on the lips and not in a drawer someplace.
I've been around professional-level brass players going on half a century and I've seen so many different positions that I can't get very excited at trying to come up with ONE best position since it flies in the face of my experiences. (If I understand the initial post, that is. Doesn't mean the subject isn't worthy of speculation, either. Just . . . not for me.)
Oh yeah - Mary Ann or Ginger? Are you kidding me? I still can't decide on Veronica or Betty.