Having said the above... I would like to re-iterate for the fourth or fifth time in this thread that the
lack of penetration is the precise reason
why I choose to keep it at the ready here.
Granted, there are other options in all common calibers - plenty of 9mm, 40, and 45 loads available that penetrate < 12".
But given the choice between handgun and rifle, if I'm going to bring a gun to a potential gunfight against an intruder, I'd rather have the rifle nearby. More stable, more accurate, et. None of my other rifles are nearly as compact or fast to get on target (my FS2000 comes close, but I'm not shooting 223 in my house, ever.)
The low-light sights really sealed the deal. When I had my old PS90 with the donut-of-death-crap optics, it sat in the cabinet. I MUCH prefer that 2nd gen PS90 sight over the tritium sights on my Glock 21 or even an Eotech (don't have to hit a button to turn them on or fiddle with brightness to turn them down...)
For the same reasons (penetration) when I travel and stay in hotels, I pack along the Five Seven. You *KNOW* any direction you shoot in a hotel, except perhaps out a window (which doesn't really fit with a defense purpose), will potentially have a person occupying that space. If I need to defend myself, I want enough to put a hole in an assailant but want to keep the chances of over penetration to a bare minimum.
Could pull of the same thing with 45ACP, I'm sure, as there are a lot of rounds (hydroshock comes to mind) that penetrate ~9" in ballistic gel, but the real world isn't a block of gelatin. Heavy 45 rounds carry with them
inertia - they will retain more energy THROUGH objects than lighter rounds will.
So for indoor use, where you're worried about what might lie behind the wall, a lightweight high velocity round makes a heck of a lot of sense. Sure, 5.7 and every other bullet that has enough energy to fatally wound someone WILL go through a wall, but the lighter bullets will shed energy MUCH faster than heavier bullets.
Just my .02.
Didn't really expect to get quite THIS involved in a conversation about the cartridge, but I always enjoy a good debate. There's a lot of pros AND cons to any cartridge/firearm, it's really all up to the individual to decide what fits their desires and needs.