The reason I say it because, yes Joe Frazier was better than Morrison, that is probably why everyone is going with Frazier, but it isn't about who's better, it's about simply the left hook, and IMO Morrison's was all round better than everyone's, he could counterpunch with it, he could time people, he could catch people off guard and the speed he could leap in and still keep his technique, he could throw it short an up close too, Joe Frazier's was brilliant, but he couldn't leap in nowhere near the speed Morrison did, and sometimes Fraizer's was wide and sloppy, he relied on backing opponents up an throwing when they had no room to move, Morrison could close the distance in the blink of an eye
They are all top pros, so their execution of the punch was just as good as Frazier's. That's why I said power is what makes the difference.
Timing, countering, lead, anticipation, speed, being able to reset quickly (Great balance) to fire it off again against a moving target All of these are different aspects of the left hook. Why are they important? Would Tua be able to land the left hook on prime Ali? Or would he miss repeatedly like Liston another powerful left hooker with better foot speed (Than Tua) and better skills all around. The left hook is probably the most complicated of all punches to land properly and consistently.
If the lefty is fighting orthodox. (As most were, especially beyond 20yrs ago.) they have the same issue
Frazier's was insanely accurate, with plenty of speed and power. It won and kept him the heavyweight title (though I notice his actually-really-good right is consistently overlooked). There's never been a left hook as good as Frazier's imo. Morrison had an excellent hook, but I didn't see him land it as accurately as Joe, and he often looped it. I don't put Tua in the same stratosphere. Iron Mike had a great hook, too...certainly not far away from Joe's. Holyfield's wasn't the most powerful, but super tight, fast, and he seemed to really creep up on people with it. They wouldn't see it coming (very important).
Ali’s own susceptibility to the left hook (prime examples v Banks and Cooper) meeting Joe’s singular excellence with that punch was never going to make life easy for Muhammad against Joe. Anything just short of the great chin Ali had would’ve seen him put out. Joe was beat up in Superfight I but Ali’s jaw was crazily swollen from the repeated left hooks, so much so, they suspected it might’ve been broken. Joe Louis had the same type of damage on the other side of his face from Max Schmeling landing the right hand incessantly.