and will overpenetrate at times. The key is to use quality ammo. Use hardball in either a 9mm or a .45 and you'll get the same results. . .overpenetration.

Stating that the .45 will stop in the target's body and "hit him so hard he won't get up the vast majority of the time" is misleading. All of this is dependent on the type of firearm being used, the distance from the shooter to the target, the type of ammo being used (.45 ammo can vary greatly, sectional density and bullet construction is key here), the emotional condition and body mass of the person hit by the round (even the physical fitness of the individual plays into the equation). Center of mass hits with a .45 don't guarantee that someone will go down and stay down.

Equally, stating that the 9mm "can and most of the time will pass right through a person and continue to hit whatever it is behind it, not transfering enough of the energy to what it hits first to stop it" is not accurate. Like the comments on the .45 above, it's dependent on a wide range of variables. A 9mm can be as effective as a .45 for home defense if, as above, quality ammo is used.

If you're concerned about overpenetration and consider the 9mm not to be a realistic choice because of overpenetration, I'd suggest you not use the .40 S&W. The difference between the two with standard loadings is not great at all. The difference in diameter is about 1mm and given standard 135 grain loadings, the muzzle velocity of the .40 can be as much as 100 to 150 fps faster than the 9mm.

In reality, any of the common centerfire calibers will be fine for personal protection. I'd consider 9mm the minimum.

More important than caliber is training and shooting skill.

IMO