Well it is my opinion that it is important to get these facts right.
OK, who else thought that EM-2 rifle looked crazy?
So...instead of talking about the history of the assault rifle and what differentiates an intermediate cartridge from a "true" rifle cartridge from a "high powered" rifle cartridge, maybe we could adress the OP's question?
First, I'll start by agreeing with what a number of people here said...the best weapon for home defense is the one that is in your hand when the zombies break your door down. If you have a choice of which weapon to grab, pick up the one that you are competent with. I'd prefer to defend myself with a Ruger 10-22 that I had put 1000 rounds through than a 10 gauge full-auto shotgun that I've never fired. Being able to efffectively operate the firearm and put rounds on target under stress is going to be the determining factor when the excrement contacts the forced air ventilation device - not who has the "highest speed lowest drag" solution.
Second, I'll say that when loaded with the right sort of ammo I can definitely understand choosing something in the AR-15 family for home defense. Provided that the operator has trained with and is honestly proficient with both options, here are a few pro / con points for AR-15 vs. Shotgun
Areas where the AR-15 loaded with suitable ammo has the advantage:
-More rounds available
-Less felt recoil per round, so likely able to get the rifle back on target faster
-The ability to defeat soft body armor (yeah, I know that this is a stretch, but someone's going to mention it, right?)
-Easier to engage targets at distances over 25 yards (this may or may not be relevant for HD - it all depends on where you live)
-Easier and faster to get more rounds into the gun if you need to reload
-less likely to penetrate multiple sheets of drywall
Areas where the shotgun has the advantage:
-Greater chance of stopping a badguy with a single round
-Buckshot spreads - so small errors in aim are less likely to result in failure to hit the target
-Ability to use "select slug" drill and shoot through moderate cover to engage a target
Personally, I don't see enough "advantage areas" for EITHER firearm to make this an "open and shut" case for most people. I'd say that unless there are specific circumstances that make one of the two options a clear winner, the answer is "yes - they both work".
Regarding pistols....if you're competent with a pistol and not so competent with a long gun, then absolutely choose a pistol. If you've stopped an thought about it and you are not going to be in a position to effectively employ a long gun while defending your home, the absolutely choose a pistol. If you're competent with both pistols and long guns, then I'd say choose a long gun. Why? The honest truth is that almost any long gun will outperform almost any pistol when it comes to making badguys stop doing bad things. And please, PLEASE do not start talking about the failures that 5.56X45mm military rounds have had in the past to stop hostiles in war zones - if you do your research and look into what really happened, you'll find that the cause of those failures is not relevant when talking about a carbine loaded with appropriate ammunition at ranges under 100 meters.
My personal choice for HD is an AR. Why? I'm more competent with the AR family than with any other firearm - mostly because I've put more rounds through that AR family than any other firearm. An AR that is properly configured (a light and good iron sights or a light and a good close combat optic with iron backup sights) will handle everything that needs to be handled inside 200 meters.
If we're done talking about AR's and shotguns, I'd like to state my opinion that Kim Kardashian is a paragon of moral virtue and a great role model for young women everywhere. I believe that's just as valid as stating that .223 is a high powered rifle cartridge.
It is a high power round, DiFi says it is so its a fact, just like everything else she says...
On the topic, I am less than comfortable moving about in a dark house with a long gun. The AR stays in the safe for a larger SHTF scenario and I am defending outside on my property. With training, I would feel better indoors and would actually prefer the AR. Until I get it, though, the wife and I are sticking with our nightstand guns. Of note, hers has a rail mounted light/laser, I have handheld flashlights on my nightstand next to the pistol.
I can pretty much say with confidence, that if anyone ever actually takes a defensive carbine class (instead of just spouting pure conjecture), I pretty much guarantee you will look at the AR-15 in a much different light as a viable, if not superior home defensive platform.
I am convinced, through a lot of research, as well as my personal experience via APT Acadamy's defensive carbine course and years of other practical experience with it that the AR-15, is an excellent choice for home defense. Especially in carbine configuration with a 16 inch barrel and a collapsable stock.
I've had a Colt AR Govt. carbine for over 25 years and for the last 10 or 12 years, it's been an integral part of my home defense arsenal. While I won't go into how much ammo I have for it, I will say that I have 3 mags full of Hornady TAP personal defense rounds for my home defense role. One in the gun ready to run and a Double Mag pouch with 60 more rounds on a sling. I have no doubt 90 rounds will handle any home invasion.
Now I believe in having choices, and in all actuality it's going to be a matter of which weapon I have at hand, and choose to use at the time of the encounter. At night, my AR is right inside the bedroom closet about 2 feet from the bed. I also keep a Mossberg 590 A1 with 20 rounds of buck shot and slugs mounted on the gun (8 in the tube and 6 on receiver mounted Side Saddle and 6 slugs in a buttstock pouch), sitting right next to the bed or in the closet next to the AR. I also have a M&P 9mm and two 17 round reloads at the bedside.
A guy here (lived in the country just a bit outside of town)...... home invasion with 5 guys.... first 2 he saw coming in the door armed and yelling threats in the middle of the night (he had heard a noise and went to check on what it was, when they broke thru the door). He had an AR for home defense..... he won, they lost. This was nothing but 5 guys who thought he had money (guy in later 50's) and a lot of things of value that they wanted and needed to steal from him.
Could he have done the same thing with a handgun, or shotgun ? Maybe. But it was sure effective ....
I know of a case we had, where almost "exact" type of situtation occurred.... he had a .45 cal 1911. Same stuff, late at night , 5 guys doing a home invasion to rob him, lived just outside of town.... even ages of BG's (younger) and him (later 50's) was about the same. He had a much bigger battle and was "lucky" he made it thru it.... as he had to physically fight the last 3 to get the door shut .... as his 1911, only had 10 rounds, and it wasn't enough.
So, does mag capacity count.. yep. The fact it's a .45 cal "take care of it" , like some say .... nope. He never "missed" with any of his shots... he just needed more than he had to stop the attack.
When people want to ban mags due to capacity, when they want to ban certain types of guns, they are also not considering the home invasions, having mutiple attackers coming at you , etc. And , BG's are "grouping" more and more when committing their crimes. But, I think they just want us to be cooperative victims.
I will add; when we were reviewed these 2 incidents..... a lot of us changed our home protection approach ... and thoughts.
I took a class on the Ar /M4 it was a very ,very long one. We got to try them out in the real world. Pretty sure we figured out how to use them and what they can do.
I have a lot of faith in my Ar's and every other weapon I use to own. In my home my Ar would not be my first go to but if it was what I grabbed first it would be game on.
But that is why they call it my house and my weapon I get to do it my way.
But sense I already turned all mine in ,It no longer madders I will just dial 911 and let them take care of it.
Good, back to the OP.
I have a 12 ga pump that was purchased to be a home defense weapon. It sat by the bed for many years. Now it is in the back of the safe, hasn't even been cleaned in a couple years at this point. I can't remember the last time I shot the thing. Over time I've come to the conclusion that an AR backed by a pistol is the answer to just about every situation. I've spent more time with an AR pattern rifle than any other platform and I'd venture to say even if I never picked one up again I'd die with that being true. With the optic I have chosen for my rifle I can be effective from within the same room or to the limits of my visibility outside my home. (Same could almost be said about my pistol with the way my house sits.) I know what the 5.56 does when employed against 2 legged predators and I am satisfied that it would work very well in a home defense situation. No, I can't select slug with it to shoot through cover, but I'm not shooting at something I cannot see. If I can see part of the BG the AR will allow me to hit what is exposed.