Inside the home there is nothing that comes close to being as deadly as getting hit with nine 33 cal+ projectiles. I still have bags of several odd buckshot calibers left from my Dad's days. About ten years ago I loaded a hundred shells each of high-brass No.1, and O buckshot, and still have most of them. I like the .32 O, and .30 No.1, because I think that more slightly smaller pellets are even more effective, but this is just my opinion, and obviously I'm in the vast minority as OO buck is so preferred. Superbuck still makes and sells everything, but my guess is that they sell allot more OO than anything else. They sell plated shot in #OOOO (.380)-.500, but there is allot of dead space in those shells, and I think their effectiveness goes down.
On boardings in the Navy shotguns were standard equipment. The narrow p-ways of a ship, and the likelihood of shooting at people who are covered by corners make them ideal. A few guys could hold off a hundred in that environment with shotguns.