Still the plain fact of the matter is that few can work a single shot fast enough to do combat with someone firing a 9 mm that has a 17 round mag or more.
Okay, now, that's just silly.
If you have a shotgun, you have the range and power advantage. Rounds on target. Done.
Personally, the things I'd be comfortable using for home defense are legion. I have an AR-15. I have a Mossberg 500 with Ghost Ring sights. I have a Marlin 1894M. I have a .45 Colt Winchester 1894. I have 9mm handguns and a .357. All of these I am perfectly comfortable using, though I'd prefer to grab a longarm if I have time. BUT.
I grew up using a H&R 20 gauge. If I only had $100 to buy a defensive tool with, I might buy a single-shot NEF. I'd buy a used butt-cuff for a few bucks and slap it on the buttstock, so I'd always have reloads handy. Then I'd buy the cheapest slugs I could find, find someplace I could shoot without paying for it, and verify POA/POI. Then I'd sleep well.
If an uncoordinated 11-year-old boy with a 20 gauge single-shot can take out squirrels at 40 yards, you'd better believe the man can hit his front door at 7 yards as it's being kicked in.
Yeah, repeaters in general are better. Little bit of practice, knowledge of your surroundings and good tactics, and a single-shot should serve fine unless you may be facing an entire team of attackers.
(And you know...for the life of me, I don't understand when otherwise sane-seeming gun folk talk about "pointing guns
at invaders". You don't point guns at invaders- you SHOOT them. It doesn't matter what they're armed with, unless they engage you outside your effective range. You SHOOT them. So they have 16 more rounds than you. So? Unless they somehow use those rounds to deny you the opportunity to fire, what difference do those 16 rounds make? Are they going to be firing as they invade your house? What the hell?)
John