While I am no 'expert' I've been a duck and goose hunting guide for the past few years. I've seen and shot A LOT of different shotguns/loads.
What do you mean "tell a difference"?? In performance on ducks or recoil? Performance, 3.5" is better hands down, no question. As for recoil, both guns mentioned are auto, unless your a 10 yr. old girl recoil shoundn't be an issue.
Seen many autos jam up and handed out a back up 870 on numerous occasion. I personally will use nothing but an 870 super mag if for no other reason than dependability. Weirdest story involves the said Beretta Extrema. A goose I shot landed the pits down from me right on to a clients gun! It was toast. Does that mean an auto is more fragile than a pump? Not sure.
If you goose hunt and get dirty, auto isn't the best way to go. While I can't question that an auto is way better for follow uo shots, I will still pick the pump 'cause I've seen autos die, never a pump.
I'll vote for the SBE (Benelli) better system in opinion, if you must go auto.
We do I lot of combo hunts ( duck and geese) as such I load up 3.5" BBB lead & 3.5" #2 HeviShot. Go 3.5" on shells, HeviShot makes a world of difference, definitly worth the price!!!