- Can shoot it with one hand, leaving the other free for cellphone/flashlight.
I prefer a weapon mounted light for HD. I dont want to start a weapon mounted light debate however. As for the phone you don'd have a tactical blue tooth at the ready? I am of course just kidding about the latter. That said would prefer quickly take up a position to cover the stairs while someone else calls 911. If that is not an option or not needed because I am alone I would likely hunker down behind my bed with the shotgun pointed at the locked door and call 911. If someone comes through the door the probability of a hit would be extremely high even with one hand. Higher than that with a pistol with one hand (speaking for me personally) and I would likely just drop the phone and use two hands.
If one handed operation is a must, perhaps in order to carry a very small child. I would still rather have one of my bullpup rifles. They can both be fired very easily and accurately with only one hand. More so than a pistol IMO. The one has a 42 round magazine and fires a more power round than most pistols. The other has a 50 round capacity.
- You can't really answer the door to strangers with a shotgun.
Here you are mistakenly assuming that A) having a pistol and shotgun are mutually exclusive and that B) because one or the other is worse for one task it should not be used for others where it is vastly superior. Besides answering the door a shotgun is a pain in the butt to lug around the house. I also like a pistol nearby because lying in bed I'd have a hell of time using my shotgun to defend against someone right on top of me. This is an area where a folding knife may be the easiest and quickest thing to deploy, I have it as an option but that doesn't mean I ought to give up the pistol or the shotgun A pistol is an important part of HD because it is easy to keep on one's person at all times. Just because I do that it doesn't mean I will (or must) sacrifice the option of a shotgun for other tasks that it is vastly superior in.
- Shotgun is harder to maneuver around hallways and corners
I wonder why swat guys don't use pistols? Now some people have have differing needs and home plans but A) I don't plan to go about clearing rooms. I plan to cover the stairs while the family congregates in one room with a locking door and then retreat to that room. If someone starts up the stairs I would greatly prefer sending 9 pellets of 00 Buck down at them or a 435 gr slug than a 115 gr 9mm projectile.
B) I do not find the length of a 18-19" barreled shotgun to be a huge problem or greatly hamper me in this area.
- You get 15+ shots with a pistol
This is assuming you have such a pistol and that you live in an area where you are not limited to 10 rounds. Even if this is the case for a person such as yourself my shotgun has a ten round magazine. Ten rounds is most likely enough for HD particularly given the effectiveness of each round and the increased hit probability of a long arm. If it is not I have a second 10 round mag ready to go. Ten rounds of 00 buck means 90 projectiles that are close to the power levels of a 9mm. 10 slugs is a level of power that is rather formidable.
I would also prefer a carbine with 30+ rounds if magazine capacity were the number one issue.
- It's much harder to try and wrestle a pistol away from someone than a shotgun
As was stated earlier this is debatable at best.
- You can keep the pistol in a small handgun safe by your bed, if you have kids. Harder to safely store a shotgun and have it ready to go.
I would rather keep it on my person. That way it is ready to go and secure from curious children. IMO it is very true that young children change the dynamics of what is safe storage. That said one could use one of a number of options to secure a long gun.
- There are more places to practice with handguns. Both of the ranges near me don't allow buckshot or slugs.
If one will practice regularly with a handgun and not a shotgun that is actually a very good reason to pick a handgun over a shotgun. The best reason mentioned in this whole thread. Being able to use your firearm well is vastly more important than what your firearm is.
A pistol may be better for your specific circumstance. I still believe that generally speaking a long arms is superior for HD. As you pointed out though and people would be well served to consider a pistol is much better for certain task and easier to keep with you. I'll better defend my self with a .380 pocket gun that I have with me than a shotgun that is on the other side of the house.