Argh, I can't believe I'm wading into this mess. First, those folks on the bank films are rank amateurs good or bad guys irrelevant. Where do you think we get all those "29 shots fired, Nobody hurt" headlines from. They have no training or have given no thought to gun handling beyond what they picked up in a Clint Eastwood movie.
Why two hands in a modern isosceles is good.
-Base of movement. Centered in a fighting stance you can go any direction easily, including running forward. Now if you are flat out running away, suggest you not shoot and save your ammo until you can figure out an effective way to use it.
-Recoil control. There is no one that can properly fire accurately as fast from single hand as they could properly trained with two. No grab the wrist, no teacup, no push-pull BS, properly.
-Orientation to the threat. With peripheral vision you have about 280-300 deg of view. why not put the threat in the center of that instead of blading your body then turning your head.
-Armoring the boiler room. With body armor you want to put the plate towards the threat, not the armpit. Without body armor two arms and a gun in front have absorbed a lot of otherwise fatal hits.
Now with one hand you:
-Can't shoot fast.
-Open your body up to a nice easy shot in through the ribs.
-Can't move as easily in any direction while keeping the gun on target.
-Will square off on threat recogntion then remember to turn, turn head and aim? Not likely.
"Too long to set up"
Damn, I'm doing it wrong. Game or not, if it took too long to set up nobody would be using it in practical shooting. Learn all hands, practice them, just don't handicap yourself by default with an inferior method and BS yourself into thinking it's all roses. Yes, that was the way it was done when your dad learned to shoot as a cop. Between then and now we've had this Applegate fella, some guy named Cooper and years to perfect it all.