Almost none of it. See my MP5 comments.
I'm not opposed to a pistol caliber carbine as a HD weapon. But as stated, that 9mm round will overpenetrate. It's a weight and velocity thing. A normal FMJ .223 round going at anything above 2,400 FPS (I may be incorrect on that speed, might be a bit lower) will or should fragment. Same goes for a a lot of the lighter HP designs. Once you get into heavier bullets like 70 grain and above, you could see some overpenetration.
Long story short, a lighter bullet like a 55 or 62 grain dumps a lot of energy when it hits. That's why varmint rounds are so light and devastating to small critters. All that energy is dumped almost immediately. A pistol round, while going fast, still retains a lot of energy and will continue moving until that energy is spent. Even "fat and heavy" .45 ACP rounds take a lot to slow them down. HP designs help in this regard, but most homeowners will end up buying a pack of WWB FMJ loads and call it good.
A pistol caliber carbine is better than a shotgun and a shotgun is better than a pistol which are all better than a sharp stick, but not my first choice honestly.