Holmes liked to box on the outside. He could get agressive vs larger opponents like Cooney but he liked boxing on the outside usually. So Louis takes center ring. Battle of jabs will be very close. I don't think either guy will have a huge edge. Holmes threw his jab more often so he likely will land more. But Holmes also had a habit of dropping his left after jabbing so sooner or later, Blackburn will instruct Louis to nail him with a right hand over the top of the low left jab. Close fight. Holmes will throw more and likely land more but Louis has the bigger punch and if he can capitalize on Holmes's mistakes, he can win it late or perhaps a decision in which he scores 1-2 knockdowns.
That right hand over the top, of Larry's jab, would be the worst thing going for Holmes. I know he had great recovery, even against Tyson he getting up, but he really doesn't want to be constantly nailed by Joe's right.
If Louis could pick up Larry doing the same thing repeatedly he could time him no question. Holmes jab would be landing alot in the meantime. Very interesting fight. M y own view is that Louis wins the first fight by late stoppage but Larry wins a series of fights. Holmes would learn from the first fight. He would pay to learn though.