Yes the problem the FBI had going to the 40 S&W was that a lot of people couldn't shoot it very well. I owned a S&W Shield in 40 S&W. I could shoot it well but did not enjoy shooting it at the range. I believe in practicing with what you are carrying and I prefer to enjoy my practice sections. Traded it for the Shield 9mm which is a good shooter but as I love my 1911s in 45 I bought the Shield 45. There is a lot more to this caliber thing then just poking a hole and bleeding. The foot pounds of energy that is delivered to the target has a lot to do with stopping power. Before starting to sound like BD I will drop stating my opinions about the subject. Yes I have read most of the data and reports and most prove the point they are wanting to prove.
I don't carry a gun at all, I have guns for home defense, but except for practice and range shooting they don't leave the house, having said this I do find the subject to be interesting
just for kicks check this out - murderous attacker who simply would not go down, even though he was shot 14 times with .45-cal. ammunition – six of those hits in supposedly fatal locations.