Size of shot does not matter, it’s the weight and velocity that contributes to recoil. If you shoot 1 ounce of #9 shot (itty bitty) or 1 ounce of buckshot at a given velocity, the recoil will be the same. It all comes down to weight of gun (heavier will recoil less), weight of shot charge, and velocity.
Some semi automatics will have less perceived recoil due to part of the cartridge’s energy being expended to cycle the gun.