Personal choice based on economics, ammo, shared use by wife or children etc. would be (and is) a good 20 gauge pump with a relatively short barrel. I enlisted in 1965. One of the things they said repeatedly in training was that no matter how well you cared for an auto or semi someday,somewhere it would jam. I own a couple of semi's but for survival I will go to my wheel guns, pumps, levers, and bolts. Before all the disagreement starts I will add that semis will be my FIRST line of defense . I will always have my manually operated guns as back up and for family members should it be neccesary. To get back to your q though, A 20 pump with a short barrel will swing well in a confined area and will be a food getter as well as a defender. If you NEED to hand if off to a less experienced member of your group they will do better with a 20 than a twelve.