I would give almost anything for boxing at the top level to return to a rule where all world title fights are decided after 20 rounds... we see more fights decided before going to the judges... we get to see the elusive boxers really have to dig down deep to keep of the maulers... in fact we will get to see the return of the truly great maulers and sluggers... overall boxing would be far more exciting on average. Great boxers can still win the fights but as I said they have to stand and fight eventually and then we see which of them is the real deal..... No more Mayweathers is my prediction, hell Manny probably wins that if it went 20.
I would prefer 15 round championship fights, as Hagler called them ,"the championship rounds". Beyond that I think we are getting into bouts that may be decided on stamina and durability alone. Apropos of your other post Harry Greb with his unparralled stamina would have been severely disadvantaged in the shorter bouts. The likes of Henry Armstrong would also shine in the longer matches.
Anything under 10 rounds I don't count as relevant history wise tbh. I also don't hold nd losses against an opponent, but I do credit those with favourable write ups.