One of the benefits of a 223 is that god, it tears up a lot of tissue when the bullets break up and go their separate ways, and there is a bit of blow out of veins and organs from the temporary cavity. It stretches, and the speed and energy it is struck with is enough to break up all but the heaviest of tissues and cause bleeding.
No, a round hitting three inches from a kidney isn't going to damage it, it's tougher than you would think. Same with the liver, it's amazingly flexible, but smack either one of them less than an inch from point of impact, just the hit from the pressure or shock wave will be like hitting the body with a ball bat.
So you have heavy bleeding going for you, and the fact that you'll have a half dozen small, sharp pieces ripping through and causing bleeding. I don't think that a typical 223 hit is reliably worse than a heavy hit from a pistol as far as bleeding, but again, that heavy, hard shock just from the bullet shock wave is damaging. Look at prairie dog videos, and imagine that happening in a body. A stud or sheathing is more than a match for a 223 that will break up, but any decent handgun meant for SD will pop through even an exterior wall with only sheathing and typical siding. Now, with vinyl and tyvek, with sheathing, it might as well be blowing through a baloney sandwich.
I still recommend the 40, for reasons I'M not going into. Not enough time and too much controversy. The choices are pretty clear, I feel that the 40 will be inferior to the 223 in disabling power, but that's not the only consideration when someone has kicked down your door, or you are presented with some other threat. I'm probably only one in five that will make that decision. It's a hard decision and depends a lot on your own home, and the homes that will be within your line of fire. Living on a hill top, with stone and brick nearby, make it locally safe, but otoh, i've still got hundreds of homes, a thousand or more people downrange, that will be wide open for those rounds as they drop. will they hit a tree before then, a retainig wall,m drop to the street, maybe even miss the houses and slam into a stone building downtown? someone who fires a twelve gauge slug downrange in a situation like i have would be nuts. an individual round of buckshot wouldn't be very dangerous down range, but hey, will it be safe to send fourteen high velocity round balls randomly into the residential district?
So much to worry about. It could drive you nuts.