Well the new HD rounds are being called "duplex" as they are a combination of two different pellet sizes, something that I've experimented with for years since I first read of Buck & Ball loads in muskets during the F&I and Rev War period...
#2 Buck and #2 Bird work great together
#4 Buck and #B or #1 Bird work well...
#BBB is best of all with either of the above two--damn hard to find though!
#F and #2 Bird are devastating on coyotes/foxes/feral dogs to 30 yards
#TT and #BB work nearly as well
#000 Buck works best with #2 bird
#0000 Buck works best with #2 bird as well...
The statement of physics is correct, 1.5 oz of bird, buck or slug will recoil with the same velocity but will NOT hit with the same energy and it is being displaced over a greater amount of surface area...Granted at 5 to 10 yards, (typical room distances) it really won't make much of a difference but what if you live in a long ranchhouse and the armed BG is breaking in to the garage 15, 20, 25 yards away from your bedroom and coming through that door...
I hate pump action shotguns with a passion and my HD gun is an exposed hammer 12 bore Rossi Coach gun for me and each of the daughter's rooms (4) and beside my wife's side of the bed is a 20 bore version of the same gun...Left barrel is loaded #2/2 and right is #4/2 and depending on distance is which barrel gets cocked first...If something does happen, we all congregate in the twins room as they are directly at the end of the hallway and offers the best field (lane) of fire...
There is one fallacy though for HD that is constantly bandied about and that's about slugs...If you want to shoot a horking big single projectile at the miscreant then get a rifle or pistol as you no longer have a shotgun but a rifle--whether smoothbore (old days called a musket) or rifled don't matter as your penetration will be the same as with hunting rounds out of a rifles or hollow points out of a pistol and no they're not frangible in the least!
A shotgun projects a string of shot that the target collides into...you do not aim a shotgun but point it as there isn't a rear sight--excluding ghost rings etc. for "tactical" pursuits by LEOs or military who might have to take out an engine block or two which we as home defenders damn well better not do--no longer Casrtle Doctrine!
N.B., All HD rounds are either lead or copper plated lead, no Bismuth, steel, Hex whatever, just lead...
I had a saddlemaker make me a barrel sleeve--keeps your hands from getting burned from hot steel or frozen with cold steel, that included a loop to secure a small hi-intensity flashlight as that is one "tacticool" device that any and every HD gun should have...He also made a Cobra style sling and a slip on, tie up recoil pad with raised cheekpiece and shell loops for the butt but those aren't necessities but makes it easier to carry in the filed when hunting...