While I still own a couple of 12 gauges I almost never use them anymore. Ammo is so much better now that a 20 gauge can pretty much do whatever a 12 used to be able to do without the pounding. They’re lighter too. As Steve said with TSS shot, you don’t need a 12 for turkeys. I’ve shot a half dozen of them now with a 20 including one over 50 yards after switching a few years ago. I’m older now, pushing 60 and not as strong as I used to be so the weight of a hunting gun really matters now. Unless you’re a goose hunter too, get a 20. People think “more pellets” and it’s true the 12 has more but the pattern size is the same between the gauges.
Manufactures are noticing the switch to sub gauges and even the 28 gauge steel upland ammo is priced exactly the same as the 20 at sportsman’s warehouse and it’s in stock.
I have an O/U and SXS (and a few semis) but I’d recommend a semi auto for all around use, they’re just more versatile and easier to reload on the run. A Benelli montefeltro can be had for around 1000 but there are 600-800 that are pretty good. There is a guy on you tube reviewing shotguns, I forget his name, he’s and exhibition shooter. I think he’s said the Weatherby semis are good too. Someone mentioned Eastern Europe and I’ve bought a few guns produced there like CZs rifles and Dickinson shotguns and they’re excellent now. If you’re tall a 28” will balance ok for you but if average height or shorter get the 26” in a semi. A 28” is ok for an O/U because the receiver is shorter.
I edited to add the link to the guy who reviews shotguns. Pay attention to the difference between Gas and Inertia guns: the Gas guns shoot softer because of the gas system but are heavier, the inertia is lighter and easier to take apart and clean. The market trend is towards inertia guns. He is reviewing waterfowl versions, mostly 12s, but you can extrapolate because most brands have lighter 20 gauge upland versions (except browning)
Frank