For the proverbial scattergun standing on the corner, I prefer a hammer double with double triggers. The hammers (obviously) serve as a de-cocking mechanism, which means the gun can be stored loaded but with no unnecessary tension on any internal components. And they just as obviously provide visual indication of the gun's readiness to be fired. Inside the house, I load #8 buckshot in the right barrel and a 525-grain Brenneke slug in the left. The buckshot is for when I want limited (over?)penetration and the slug is for when I don't. Double triggers allow me to select the proper tool for the job on the spur of the moment, and a lifetime of upland game bird hunting with my granddad's LC Smith assures I'll never get the triggers confused. So my choice was the 'Hammer Coach' made by Huglu of Turkey for CZ.
Barrels are 20" so you could lop off a couple of inches and still not run afoul of NFA territory, but it's a slick and fast-handling smoothbore as is. It's spendier than the Stoeger but heft the two side-by-side and it is evident why. The ShayZed is an heirloom-quality firearm. All double-barrels, be they smoothbore or rifled, tend to be spendy because it is not an inexpensive proposition to join two barrels together such as they both shoot to the same point of aim. Even the plainest of double rifles, the sort that are standard equipment for African professional hunters who guide tourists in quest of dangerous game, are eye-poppingly expensive because the task of "registering" the twin barrels both to shoot to where the one set of sights is pointing requires considerable attention from a skilled double gunsmith. Some of the most masterful executions of the genre have been the 3-barreled "Dreilingsgewehr" survival guns built by Sauer for the Luftwaffe. Issued to pilots in the North African theater, the "Drilling," as it has become popularly known, has twin smoothbore barrels with a centerfire rifle barrel nestled underneath. One in good shape, with case and all accessories easily will fetch mid-five figures today, as much for its artistry as for its role in a dark period of history.
Great write up! You should do it for some of the shooters' magazines. You got the talent. I have a modern in expensive Chinese copy onto which I have drilled and tapped a couple of useful picatinny rails above and below.
BTW, unless you think you'll be facing a Kodiak Bear, the Foster slugs are as effective as the Brennecke at half the price.