Let's face it...none of us here are experts on these things. But FWIW, my brother was on the force for 13 years, and he said that he did not even feel safe at all when they made him carry a 9mm pistol. He said that there was a shootout between the cops and a perpetrator wanted for armed robbery, and driving a stolen car. The cops shot through the back window of the car, but the perpetrator escaped initially. Later on that day, they caught him and when the car was examined, they found 9mm bullet heads laying on the back seat. The 9mm crap didn't even make it to the front of the passenger compartment after going through the back window!!
There was another story about a shootout and the perpetrator was a big fat guy. The cops shot the guy 5 times in his gut with 9mm pistols, and all five shots didn't even get passed the guy's fat layer. He had to be tackled to the ground.