I recently took a long gun tactics class. Lots of shooting from odd positions, around barricades, while moving, and in scenarios (starting inside vehicles, running to cover, etc.). We shot each drill with a shotgun and a rifle.
My shotgun was a pumper, and my rifle was a fairly heavy 16" AR in 5.56. Even though the gear I used isn't what was laid out in the OP, perhaps the lessons I learned from that experience might be useful.
My conclusions:
within pretty broad limits of terminal effectiveness
shorter, lighter, bigger ammo capacity, less recoil and noise, and easier operation
beats
longer, heavier, smaller ammo capacity, more recoil and noise, more complex manual of arms
EVERY time.
My ideal tool for these tasks is an AR sbr in 5.56 (or a lightweight PCC sbr), without a can for training, and with a can when used for real. Plus lots of training and practice with that platform.
Buckshot, slugs, and rifle rounds like .308 might be at the top end of what is considered to be acceptable terminal effectiveness, but I don't judge that benefit to be anywhere close to the importance of short, light, high capacity, less recoil and noise, and easier manual of arms.