[Wreck-n-Crew]

The ability to have more round capacity is the reason for the 9mm preference among law enforcement due to the fact that more rounds means better chances in a shootout.

But when police get in a shootout, usually the suspected aggressor knows that gunfire is almost certainly be returned and most citizen encounters rarely end up in a long shootout because the aggressor usually expects to have the only gun, the element of surprise and the upper hand altogether and doesn't want a shootout.

Also in the case of citizen self defense, statistics show that these gun battles usually don't last as long as someone prepared mentally for a shootout because the majority of offenders find self preservation, a basic instinct to flee (if possible) the norm once bullets fly . Therefore the round capacity is not a definitive factor, but usually a just in case factor for concealed carry and home defense scenarios.

That is why the 9mm has the all around sidearm preference among most law enforcement and citizens. The balance of stopping power, magazine capacity and accuracy at distance due to lower muzzle climb than most guns with more powerful rounds. But there are preferences in handguns for a reason, personal preference to the belief of ones needs in a self defense scenario.

I for one love my 40 S&W and prefer it because of the stopping power. The fact is that the 40 has more stopping power because it has more mass with the about same velocity as the 9 and about the same penetration as the 9 leaving a bigger hole and a harder impact due to kinetic energy.

IF you know anything about the effect of kinetic energy it is the x factor when comparing the 9 and the 40.