Shotgun. No wait. Revolver. But the shotgun is more versatile Change the load and you can hunt just about anything. Revolver can almost match that though in .38/.357, except for wing shots. Hey I don't hunt anyhow, so screw the scattergun. But just look at the 12 GA SxS with 18 1/12" barrels from the business end. Just the thought of that pointed at me gets me makes me queasy. But that's only 2 shots, the revolver has 6. What's a gun nut to do?
BUY BOTH Both isn't an option according to the rules of the question so a choice has to be made. ( Luckily real life isn't quite as harsh 
I chose a revolver. Smith and Wesson model 66 with 2 1/2 " barrel. My reasoning for the choice, it is a defensive weapon, and a defensive weapon only. What you see is what you get. No target frills, nothing to dress it up.(except some planned action work) nothing to interfere with why I bought it. My idea of home extends beyond the confines of my house, by that I mean when I go camping or travel. The shotgun is too large to carry. At this point I must add that I do not illegally carry the Smith, either on me or in the car. It remains unloaded and locked in the trunk, separate from the ammo. I can get to it within 30 seconds, and load at least 2 rounds, and have them under the hammer. The shotgun takes longer to unpack, and load. An auto is out of the question. It takes forever to load anything in the magazine. A loaded magazine, here in Ohio, is considered a loaded firearm, whether it is in the gun or not. Speed loaders are a gray area, some cities here throw them in with a loaded magazine, and will press for a felony charge. Others do not. Brandishing a firearm is also a felony, so any scare benefit of the "2 big holes in the barrel" becomes a non-issue. Same goes for racking a slide to scare the bejabbers out of somebody. That is considered aggravated assault, brandishing a firearm, and if pointed in somebody's direction, attempted murder. (Laws here in Ohio really suck, hopefully with our new Governor things will get better)All things considered. I chose the revolver. I may be wrong, and would like to hear others reasons for their choices.
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A free people ought not only to be armed but disciplined;
George Washington Jan 8,1790--There can be no doubt about the Second Amendment.