I've read a couple comments and it seems you want something for personal defense. A weapon is a tool and like a tool you need the right one for the job. If you live in the country or near the edge of a forest were you're dealing with long range and large wild animals, then the AK47 or an AR15 would do the job. If you live in the suburbs or in an apartment stick with the shotgun, the velocity of the above mentioned weapons will go through the walls and may kill your neighbors, you would be charged with manslaughter if that were to occur, even if you didn't mean to do it. The shotgun will not penetrate the walls so long as you buy 00 buckshot or similar.
Being a gun guy I will say if you want either rifle get rapid expanding bullets such as the Hornady Vmax. It's a varmint bullet made with a thin copper jacket so it dumps a lot of energy in the body and that's where you want most the energy. The more energy in the body the more severe the internal damage.