multitasking
One shotgun, three barrels. Mossberg 500 with long birding barrel, 18.5 HD bbl and a .50 cal muzzleloder barrel. It takes 30 seconds or less to change out. It is a gun that feels good in my hands and has been reliable as can be (once I got rid of the plastic safety).
It has killed doves, grouse, pheasants, turkey, ducks and geese with the long bbl, and I hope I never have to find out, but I presume it would hit a bad guy just as hard as necessary with the shorty. The muzzleloader bbl is just for fun, but it's deadly accurate to 100 yds, though I haven't got my best load worked out on it yet.
In my book, the best HD gun is the one you feel comfortable and capable using. For me, that's my Moss 500 wearing the 18.5 and full load of 00.