.410 slugs should be at least as effective at close range as a .44WCF; they make a .45 hole. But I think a better choice for self defense would be the various buckshot loads available. At very close range they make a nasty "rathole"; a little farther out they make a loose group, which depends on its size and shape on the choke and distance, like any pattern. But you can aim a little off and still do damage and the three 000 or five 00 pellets don't penetrate nearly as much as a single slug. So less chance of "collateral damage" (also known as shooting your neighbor accidentally).
