Djokovic's is overrated. It's probably the best and more reliable defensive backhand in history, hitting well on the move, against power and depth, but he is rarely aggressive with it. Sinner also hits well on the move but is much more aggressive, including approaching and hitting winners with it. Comparing it to Agassi's is a bit unfair though partly because they were developed with such different equipment. Agassi didn't have the benefit of polys and played against serve and volleyers so his he did it best for the type of backhand needed at the time - hitting early so that the volleyers don't have time to get to the net. But Agassi didn't hit very well on the run like Sinner does. But frankly, no 2 hander looked comfortable hitting on the move until Djokovic revolutionized and perfected it.
