plain and simple, if you want to knock the target down, you want a large slow moving bullet. You want to penetrate, you use a faster moving round.
The .45 govt. was put into use because the army found the .38 cal pistols they were using, did not work well against drugged up fighters in the Phillipines.
There is a reason the army and other people are going back to the .45 govt. slow, big bullets knock down, getting that same sized round in the hottest speed you can find causes you to loose the knock down effect.
I shoot 9mm at work and at home. It is a nice round to train with, but I would never depend on it in combat. 15 rounds in 9mm is not worth 7 in the old govt models.
This is only my personnel opinion, I do like the .40 as well. But for knock down, I go with 110 gr Semi Jacketed HP .45 Govt. I am sure there is even some slower moving rounds that would do even a better job of knock down. That is what I use after 20 years of shooting 9mm and .45 for comps, and now the Army.
I believe after a person is knocked down, their brains have more than enough time to process the pain and damage that was involved in that act that put them down.
thanks for the great reads on this thread