The only thing I know to be COMPLETELY true about shotguns is that eventually they will prove you wrong. During WWII airplane mechanics talked about gremlins, the unknown entity that made things go badly despite careful attention.
I have seen gun and shot combinations that threw beautiful patterns, print a beautiful pattern with a HOLE right in the middle of it. That is easy to discount, unless that particular shell is the one used to shoot the hundred target in a skeet competition.
There are places for both slow shells and fast shells. I had a dear friend who taught me about dogs and quail. He was the one who showed me how to open patterns with speed. His special shell was 7.5 shot over a hot load of Alcan 5 through a Winchester improved cylinder barrel. With it he had a decent pattern at 15 yards (as checked on paper), and he could literally stone a quail at 35 yards. Watching him shoot was like watching an artist paint.
