You aren’t playing for possession 3. That’s just an advantage if you make it there. On the other hand, I don’t like it that if you take the ball first, only the defense has the ability for a game ending play. So I think it really is close, with valid point/counterpoints to be made.
There is no data on it - so it’s all subjective at this point. Maybe some analytics people look at thousands of games and pretend it’s these rules - and then evaluate the % of times 1st posession wins. But even then, you wouldn’t have the 4th down dynamic, and would probably miss some FGs forfeited in lieu of punting deep. So you can’t duplicate it, but could get a directional idea.