Hearns was a beautiful boxer with a lot of power. He also knew how to THROW an punch better than most, thus getting the MOST of the power he had. Imagine if George Forman actually knew how to USE his power when he was in his prime.
The right hand Hearns hit Andries with was indeed a better "Looking'' punch because it hit him straight. Andreies was more cooperative than Duran, who was still moving his head in an attempt to avoid being hit, until Hearns Polaxed him. Andries was standing almost straight when Hearns hit him. You dont see better punches on paper.
The right he hit Duran with was certainly more destructive. You could actually Hear the punch land and see Duran's body go numb as he fell face first to the canvas, In he same pose he was in when the blow connected.
No question that was the better punch in terms of effectiveness. Usually, when a fighter falls face first, he's not getting up. The other thing to consider is that, even though he was past his prime and well above his best weight, Duran was a better Jr. Middleweight than Andries was a Light Heavyweight.
Not many from Welter to Lt. Heavy could punch like Hearns.