Lol. From a ballistics standpoint, a 12-gauge has better stopping power than a 20-gauge. But, if you dislike and/or can't handle the 12-gauge blast and recoil, you won't reap the benefits it has over the 20-gauge, but still suffer the downsides. So for some people, the 20-gauge would be a better choice. It has less recoil and allows quicker follow up shots. But if well placed, a 2 3/4" load of 00 buckshot should drop anyone with one shot, maybe two if they're all cracked out or on PCP.Yow. Load your 10 gauge with whatever the hell you want.
I'm wondering about the birdshot versus buckshot for super close quarters. I'm not at all questioning Chuck Hawks authori-TIE, but even at ten feet, I'd still rather have buckshot. It's heavier and would still do more damage to a human body IMO. Overpenetration is a concern for me as I live in an apartment with thin walls all around. Still...rather stay loaded with buckshot. Slugs are out for sure.