It’s been 12 years since my son was shooting on a youth trap league. His team shot both state and national up at Vandalia, OH ( grand American) and after 2005 at Sparta, IL. At 11 yeares old, he started and ended with a model 12 in 12 gauge. All on his team at 11 years old shot a 12 gauge as it’s all about the load you are shooting. Many used a 1 oz. load at about 1150 FPS which is considered extra light. My point is, almost all these new trapshooters start with a 12 gauge as they make loads so light now days. In fact at the national shoot, they only had about 1 or 2 pallets of 20 gauge compared to a whole room of 12 gauge shells in all flavors. If it will be used for hunting, then increase the load for hunting and often out hunting, one doesn’t notice the recoil. For cowboy action, they are using about a 7/8 oz. load at 980 FPS. This is called a low noise/low recoil load and it is super soft. And of course, if your a reloader, you find the velocity and load recipe that works for you.
As others have said, sometimes a 20 gauge gun is a bit smaller and lighter, then it can actually have as much recoil as a 12 gauge. I am using a Win. 24 ( double barrel) in 20 gauge as it is based on a smaller action and is faster for cowboy action shooting. As a funny side about it is that I load a standard target 7/8 oz. shot at 1150 FPS for it and borrowed some shells to a lady shooter and she said my shells kicked! Sure as heck, she was using low recoil 20 gauge and my target 20 gauge was loaded hotter.
Anyway, if it were myself, I would get a gas operated 12 gauge and not think twice for a recoil sensative shooter. We have started alot if budget conscious shooters with a Winchester 1400/1500 gas gun. For some years, Winchester didn’t even put recoilpads on these guns. Remember a gas operated auto kicks less then a recoil operated auto. I know as my light Franchi recoil guns have a bit more kick than the recoil guns. But those light Franchi guns are so wonderful carry in a hunting field.