I think the difference is that Holmes jab was alot harder then Ali's jab and that would be a factor as I don't see Frazier being able to walk through it. Two of my favorite heavyweights and it would have been an epic fight. I pick Holmes by split decision in a fight people would argue who really one.
Larry would have to use the jab as a priority in keeping Joe off him, relying on holding and (ultimately) the right uppercut to discourage him when he gets under it. Larry is my favorite fighter, but I really just don't see Joe relenting much. I can see Frazier getting knocked down by the uppercut sometime, perhaps early in the fight...but that wouldn't stop him. Larry would win a bunch of rounds with the jab, and get a 10-8 for the uppercut kd. But I just see Joe warming up to smoking. The 6th through 12th are his. If it's a 12 rounder, I give it to Joe close UD. A 15 rounder...Larry is known to do pretty damn great in the later rounds, and I could see Joe getting badly swelled up. But I think FOTC Frazier still takes it. Possibly a 15 round split decision, and as @Cobra33 asserted, it might be a fight argued over for years if it's that long.
Holmes' jab may have been harder than Ali's but it wasn't as versatile nor as quick. Ali could change the direction of the jab as he threw it, which was crucial with Frazier's head movement and crouching. Holmes' couldn't really do the same.
Its debatable who hit harder, but Holmes has a more diversified offense and is more active than Ali. .
I do not see a path for victory for 1982 Larry Holmes against FOTC Joe Frazier. As good as Larry was, TOO MUCH PRESSURE! Joe Frazier was relentless against boxers! And I do not see how Larry holds him off! Larry Holmes may have enough heart to survive the 15 rounds, but the decision will go to Frazier for sure, in my view. Frazier's face will take a beating. Of that I have no doubt. But Joe will just keep coming and coming and coming, and he will be throwing punches in bunches continuously! I am going with a Unanimous Decision win by Joe Frazier, but I would not be surprised by a very late stoppage in favor of Joe Frazier..