A lot of good info here so I will offer and alternative home defense mindset. I see alot of great small caliber hanguns here(many of which can double as excellent concealed carry guns) but not anything GREAT for home defense. If people(perhaps 2 or 3) are invading your home, they will prob have similar guns mentioned here. When you go to a gunfight you do not want to be on a level playing field with your opponent/s. You want the fight to be as lopsided as humanly(inhumanely) possible. Since you only need home defense, and not carry, you have the luxury of going larger. Just cause gel tests are cool..here is a 9mm gold dot in ballistic gel
Pump shotgun is devastating but not the best choice imho, because it doesnt deal well with the threat from multiple attackers. The "rack" of the shotgun doesnt make determined folks run for the hills, it just tells them where you are, and the 9mm rounds they prob have are excellent(as most things are) for penetrating interior walls , so you rack the slide and suddenly rounds start spalling through your walls in your direction because they know you are there and a serious threat and start shooting in panic through your house. Also, as those of us who have been in a firefight can tell you, once it goes kinetic in a darkened environment, and the first shot pops, things start happening fast and crazy. Your hearing is impaired by the muzzle blast, you may actually be a disoriented by it...your adrenaline dump gives you tunnel vision..your night vision is gone..and keeping track of all the threats gets really difficult. Do you really want to be wasting seconds racking the slide when 2 or 3 people are shooting at you nonstop? Also a pump shotgun doesnt give you much of an option in a hostage scenario..bad guy is scared and has a knife to your wife or kids throat..you cant risk a shot with a shotgun. Here is buckshot through ballistic gel
Best choice (in my opinion)
Pistol length, rifle caliber(I prefer 300 blackout) is my recommendation for most lopsided(in your favor)home defense. Rifles(with appropriate ammo choice) and a good reflex sight are MUCH MUCH MUCH easier to bring on target and followup shots are similarly faster and more accurate than handgun. Also each round that hits is FAR more devastating to the threat than their handgun rounds coming back at you. Doesnt really have to be pistol length but I prefer it for maneuverability indoors. This is my 7.5 inch 300 blackout AR pistol on the bottom...for comparison on top is standard 16inch 5.56 AR rifle, and my springfield xd9 subcompact(3 inch barrel) with lasergrip(that I often carry concealed). The 300 blackout round is designed for full power out of short barrels(9 inch is optimal) and having 30 rounds of devastation to accurately send to any threats more than likely will provide me SUBSTANTIALLY more power in the gunfight than the invaders. I bought the 300 blackout pistol from Palmetto state armory for $500. optic(sightmark M spec FMS reflex) was around $200, and the light was $50. magpul angled front grip was $40. the ammo is not cheap though...cheapest practice ammo is around 50-60 cents per round. The good stuff for defense will run you over $1.00 a round...but if you need it...you will be happy you have it. Also you can add a suppressor and still keep a relatively short overall length and have the benefit of not destroying your hearing when you shoot it in your house without ear protection. That pistol is also small enough to ride in a standard gym bag so through it on your front seat and roll out(for those who can carry a pistol concealed) Here is 300 blackout through ballistic gel