I reload for all gauges 10 through .410 and shoot, well used to shoot, all but the 10 gauge. Since I hurt my right shoulder years ago I started using 3/4 oz. in 12 gauge for target shooting. Most times when I used to hunt pheasants, most were pen raised, with my setter I shot a sxs 16 ga. Fabrique Nationale with 30" Krupp steel barrels. Gun weighs 6 lbs. 1.8 ozs. and is a pleasure to shoot. When I lived in Northern New Jersey I hunted public hunting grounds with a Beretta BL 4 in 28 ga. and killed hundreds of pen raised pheasants using reloads with 7 1/2 shot and 9 shot. Most all shots had to wait for them to get out there. Back when I was in Germany in 1967-68 I bought a Winchester 101 20 ga. with 26" barrels and sent it home. I did buy a Remington 11-48 in .410 with 25" ICY ventilated rib and used that over there on hares, Hungarian partridge, Mallards, Teal. The hare weighed at least 10 lbs and hung from my belt its ears were dragging on the ground. I still have those guns and have used the .410 here at home on wild quail and woodcock.
So the whole point on the merits of a 12 gauge, I don't see it. If you are not confident in your shooting ability then shoot your 12 gauge with 1 1/8 or 1/14 oz. shot but not me. I was quite happy shooting the small gauges back then and have now started shooting a new to me .410 Hunter Arms Hunter Special. I will start shooting Trap again with my 12 gauge hammer gun using 3/4 oz. reloads. When I miss I can almost always know why, not the payload but me. No trophies or money involved but pleasure when they break.