I attended the 99th Session of the FBI Academy in 1974. One day our range instructor asked the class which gun would do the most damage, a 12-gauge 870 loaded to the max with double-ought buck or a decked-out Thompson submachine gun with a 40-round magazine. Most of the class, having seen the Thompson blasting away at the Mafia in movies, allowed as to how the submachine gun certainly would be the most deadly. At any rate, it looked the most deadly with that snarky little barrel sticking out there just waiting to send a couple of dozen rounds into some latter-day Al Capone's automobile windshield.
"Well, let's see," said the range instructor, picking up the Thompson. He turned and emptied it into a target with a wooden frame, which was situated about 20 yards away. There were lots of holes, of course, because 40 rounds of .45 caliber ammo fired off over a few seconds has a way of getting a person's attention. I was impressed.
Then he picked up the 870 and turned to another target. BOOM-BOOM-BOOM-BOOM-BOOM! He racked off rounds as fast as he could jack the slide back and forth. Pieces of target and wooden frame flew all over the place. In fact, the target was shredded to pieces and left slivers of wood and paper all over the ground.
Putting the 870 back on the table, the range instructor turned and said, "Gentlemen, (there were no women in our group), don't ever sell a 12-gauge riot gun short. For self-defense, I had rather have one in my home than anything else."
I never forgot that lesson: there are more expensive shotguns, prettier shotguns, and shotguns that will equal what an 870 will do. But all things considered there is no shotgun out there that will beat an 870.
Unless it's two 870s.