You guys are acting as if a bullet through someones arm doesn't count. Have we all forgotten human anatomy? Shooting people isn't a math problem, this isn't precision reloading, it's a break-the-system-until-it-shuts-down problem.
Folks, if you shoot a bullet through some person's limb they are going to notice it. No it won't be an instant stopper but few single handgun hits are. That we've established. But you are probably going to sever tendons, disable major muscle groups, tear nerves, and that arm will be out of the fight and dangling useless and bleeding from the "Bad guy's" shoulder.
The "bad guy" probably won't even notice it though because he's going to be busy wishing he was someplace else while sucking up the rest of your magazines ammo supply. Because, "Remember kids! If it's worth shooting once, it's worth shooting a lot!" And any hits from those rounds to the upper thoracic cavity are going to hit something vital. Lungs, heart, arteries, liver, they all lie within less than six inches of the surface. Shoot a hole in a guy's upper chest and they've got a sucking chest wound right now. They can't breath and they are dying.
Look at the picture below. Unless you're fighting Jabba the Hutt or are trying to reach the "Bad guy's" kidneys from the front by shooting trough all that intestine, this 6-10 inches of penetration nonsense is hardly worth losing sleep over. .380 will reach all of that. So will 9mm, .40 S&W, and .45ACP.
Pick a premium hollow point. My choice is Speer Gold Dot out of a Sig P232. Keep good situational awareness, pay attention to who you choose for friends, and go about your business. You'll be plenty safe.