A 12ga is probably the better option...and its easy to reduce recoil by shooting lower velocity loads .. or 1 oz or 7/8 oa loads.. at 1150 fps ...especially if you reload / but there is a wide variety of shells available commercially as well.
Fit is the issue on shotguns / so they hit where you look.
Nothing wrong with a good pump gun ...but any gun like that is a fixed breech vs a semi-auto where they cycling of the action absorbs some of the recoil.
In terms of gas guns ...Beretta has a strong lineup of guns ( they make about 30 different models of semi-autos alone / different styles of combs,etc ) but in gas guns they are the dominant mfg ....Browning also makes a pretty good semi-auto in the Silver line of guns ...like the Silver Hunter. Prices are $ 750 - $2,000...
For a good pump gun option - I also like the Browning BPS ..like the BPS Hunter model...they're selling for around $ 700...
A couple of things....in general, I'd go with a gun that has a 28" barrel ...whether its a 12ga or 20ga is irrelevent.../ longer barrel gives you a longer sight plane ..helps smooth out the swing on flying targets. On an Over Under..I'd go with a 30" barrel ...receivers on O/U's are shorter than pumps and semi-autos.
Don't overlook used guns ...but make sure what you buy has changeable screw in chokes...so the gun is more versatile. You might end up shooting mostly an Imp Cycl or Mod choke as most sporting targets...but its nice to screw in a Skeet choke if you want to shoot some Skeet ...or a Mod or Improved Mod for some Trap ...
Cost of targets and shells...is what will drive your costs....long after the expense of a gun is long forgotten. With the cost of sporting targets in my area at about $40 / 100 and 5 boxes of shells at $35 ....its easy to spend $75 per shooter on a day of sporting....( and if you go 20 times a yr ...it adds up to $1,500 a yr pretty quickly per shooter ) ....so don't get too upset over a $ 1,500 or $ 3,000 shotgun ...if its a gun that will last you a lifetime.
My personal choice for a Sporting Clays gun, a Skeet gun and a Field gun ...one gun that does everything very well ...is a Browning, Citori, XS Skeet model with an adjustable comb in a 12ga and 30" barrels ...today that gun sells for around $ 3,200...but its a gun that will last for 3 generations ...or at least 1 Million shells..easily. On shotguns - and guns in general - you often get what you pay for....
But the first gun, I bought for my boys when they were teenagers...was a Browning BPS 12ga - Hunter model 28" barrel. Now some 20 yrs later...they are still solid guns / and I bought a pair of them for myself as well in 12ga and 20ga and still have them too ...even though I've gone on to other guns.
One of our buddies on here, Slugo, is shooting a Franchi 20ga semi-auto ...with very good range reports / I might add that gun to your list as well - based on Slugo's comments. But I'd also look at the Browning Silver hunter as well...and maybe a Benelli Super Sport as a comparison - and some of the Beretta 391's...( and have fun with your search ) !