Think about it, if you are choosing a gun for a gunfight, to stop your opponent and defend your own life, you would be wise to look at what special ops chooses for that purpose. Invariably, special ops forces around the world choose a variant of the M4 carbine as their primary weapon. Not pump shotguns, not full caliber battle rifles (M14, FAL, G3). Not handguns (those are "secondary," ie. backup weapons).
No, don’t get me wrong, you would be quite well equipped with a 12 ga pump, especially if you can’t, or don’t want to, spend the money on an AR. But, as I said, there’s a reason why professional gunfighters don’t choose them for anything other than blowing hinges off doors.