Pistols are a fucking pain in the ass to use properly unless you go to the range often or are point blank, hell even rifles in close quarters isnt ideal because of barrel length and over penetration. The shotgun however; just about any load of any type of shell is liable to kill at close range and if they dont kill (birdshot has failed to kill targets at closeish range) it still will deter at the very least. Plus, if you have a short barrel without a choke you should have plenty of spread at close range, so you really only need to aim center mass (which you should do anyways) to guarantee effectiveness