Those 3 1/2s with an Xtra Full choke REALLY makes a difference.
Shoot a goose in the head or neck and he doesn't know if he's been killed with 3" or 3 1/2s... Good marketing by the manufacturers...
3.5" shells are better as they have more pellets in the load so you get a more dense pattern. It doesn't really give you any extra range as the steel losses its velocity at the same rate weather youh ave a 1oz load or an 1.375oz load. The denser patter just means less criples when shooting within range