I think a lot of these discussions get off track because of some deep seated my-gun-is-bigger-than-yours farce.
I don’t think your going to be under gunned with any of them, or even a 9mm carbine. If anyone here says 9mm carbine is a pop gun, PM me and drop by for an experience with 32 147 grain hollow points, with 32 more a jungle-clipped mag away. If your shft is worse than that, maybe you’re not going to make it no matter what firearm you have. I mean really, all day long there is discussion about how the so-and-so .308 will reach out and touch someone at 300 yards and anything less is like tattooing “Candy a$$” on your forehead and then heading to a whips and chains convention. Which of course it will (range 300+ yards), but it ain’t the point of a shft gun.
The point is, what is the threat you face and how will you deal with it? I think come shft, while you will spend time in your house, and therefore gun size and weight won’t be a big factor, you will find yourself in situations where mobility and concealability count.
It is going to be really tempting to leave that big heavy unwealdy gun back somewhere where you aren’t. But to be useful the gun has to be with YOU 24/7.
As for fire power, sure in NOLA there were gun battles, but up close and not against entrenched fighters but against groups of looters. Given a situation like that, I don’t have to have a 50 cal and I don’t want to run out of ammo and have to head back to the house for a reload.
My point is, I’ll take a healthy dose of mobility, good ammo capacity, and enough firepower over massive firepower and low mobility. I think guns that fit this are pleantiful.
For our house I balanced fire power with weight and size, combined with what my entire family is comfortable with. That means (for us) ARs and Uzis. The AR is fairly compact, but the Uzi compacts that much more if needed, and my wife is comfortable with both.
In my mind the shft gun has a folding stock (best) or collapsible stock. Something you can get on the AK and shotgun. Some carbines won’t have that.
I darn well want a lot of rounds at the ready. AK with a drum is going to be hard to beat. AKs with the long banana clip don’t conceal well enough for me, I don’t know if you can get 20s like for the AR. For my AR I keep a mix of 20s and 30s. 30s for inside the house, 20s for concealability. Lone shotguns without extra rounds attached don’t cut it to me. Get caught without a real convenient reload, pop off a couple rounds, and now the only thing on your mind is how to score more ammo before running empty.
Some carbines don’t take a lot of rounds either, another consideration.