To clarify: this was mostly related to the inquiry from FALZ24, which is a drift that I took farther.
While I am better and more recently trained with the AR (thank you, Uncle Pat), I did have good foundation training with the shotgun and I am adequately comfortable with either. (My academy taught slugs as the default and buck as specialized, so ... I select slug by loading them into the tube.) As much as I hate having to take this position, I think the politics of using anything that even looks like what California refers to as an "assault rifle" or whatever their fucked up totally incorrect nomenclature is will present an unnecessary complication to the analysis of any shooting in which you are involved. That is utter shit from a legal perspective; justified is justified, but a risk worthy of consideration in your situation. It is unfortunate for many reasons, not the least of which is that the addition of useful accessories such as a flashlight and RDS is more difficult.
I harp about issues related to home defense on another forum and will paste in my most recent stuff on the topic:
1) ALWAYS CALL 911 unless it precludes the necessary response under tight time lines. Period. You want the record made that you are the first to call and express concern for your well-being. I know of 2 cases in the Spokane area (one city, one ... rural county near Liberty Lake, or maybe in Liberty Lake) in the last few years in which the encounter was recorded due to the phone line being open. In those cases, the recording showed that the complainant/victim was correct and telling it like it was, and the deceased offender was in fact the problem. Made the victims' lives suck a lot less.
2) Even under the best of conditions, LE response time is not likely to be adequate, so don't rely solely on LE.
3) Your doors should be unlocked only to pass through them. Period. Never open the door to anyone until you are sure of who they are and you know it is a good idea. Don't be afraid to yell through a locked door. For the love of all that is holy, do not go outside unless they have lit your house on fire. Stay inside, and make the offender really show that they are really dangerous. That will improve your personal and legal defense situation. If you break this rule, pay someone to administer slap therapy until you have un(screwed) yourself.
4) Layers, darn it, layers.
a) Fence of at least 6 feet as close to the property line as possible, with a locked gate. If your local code or some silly homeowner's association precludes that, move. Anyone who needs to come to your house has your phone number. Anyone who gets offended by that is probably not someone you need in your life. Beat this into your head: no one has a right not to be offended; if you are not willing to offend people who are not welcome at your home to ensure they feel unwelcome, hire R. Lee Ermey to help you overcome that problem.
b) Floodlights as needed, with timers or motion detectors as you prefer.
c) Dogs. Any dog that is alert and makes noise is a great warning and good company. Medium or larger breeds (65+ pounds) make deeper barks, and some number of offenders will be uninterested in finding out if that deep bark includes a real risk of a bite. We're rott fans; there are other good breeds. I'm inclined to Boerboels, Ridgebacks, Bullmastiffs, Mastiffs, Danes and the like. If you truly NEVER have company and can stand a dog that loves you and the rest of your household and HATES everyone else ... Fila. That's a serious commitment - Filas are not even close to public safe. Bozo wore a muzzle for a reason.
5) Gun stuff:
a) Know the law of your state with regard to defense of self and defense of home. Know it well.
b) Learn as much as you can about pre-attack indicators. Big one: Anyone who does not immediately comply when told to leave, show you their hands, etc. is likely to be a serious problem. Ask, tell, make - a 3 second or so process. Cops know this - that's why if a person does not forthwith comply with arrest/detention directions has to have an immediate application of force necessary to control them.
c) Have a good grasp of ballistic effects on humans and where to aim. (Short version: pistols suck. Plan on shooting someone a lot of times to get them to stop.)If you do not own a copy of "Urey W. Patrick and John C. Hall, “In Defense of Self and Others -- issues, facts & fallacies: The realities of law enforcement's use of deadly force” (3rd edition, 2017), buy it. Although mostly LE directed and specific, most private citizens need to understand why cops do what they do and what the legal issues are, and the ballistic knowledge and other pieces of the book can be useful by analogy.
d) Whatever firearms you own, be proficient with them. Good hits with a .22 won't be perfect, but the offender will not feel or perform better and that's better than a miss with the beast you can't shoot well. Have lights on them if possible. Both of my long guns do. Handheld flashlights are also your friend. Bright, best quality ones.
e) Don't settle for the training that came in the box.