...When I've seen people shoot buckshot out of a shotgun, whether it's a cut down 870 or a Benelli M4, the pattern is about 6 inches or so at 25 yards. Granted it has lots of killing power, but it still requires reasonably precise aiming. And you're limited to 8 shots or so, unless you go for one of the semi-autos that take a box or drum mag. An AR with a 30+ round mag is at least a couple of inches shorter overall, holds more ammo, and may arguably be easier to shoot rapidly. Granted, the bullpup shotguns are shorter than even an AR.
When there are so many good AR's around, what advantages does the tactical shotgun still have, in a defensive scenario?
