I think learning to perform the task on demand, under stress is more important than absolute accuracy or speed.
A buzzer or some competition can add some artificial stress to the situation which seems important to me.
There is always the firing line sniper shooting 1/2 inch groups all day, but add a buzzer or some competition to the mix and he does good to hit the backstop. You get the same thing with the BJJ gym assassins. They tap people all week in practice, but cannot fight out of a wet paper bag come competition time.
It would seem to me adding some artificial stress to the situation while still expecting acceptable shooting is ideal. Competition and buzzers on a time crunch seems the easiest way to do so to me.