RE: Shotgun Barrel Length...
I have a different opinion on shotgun barrel lengths than most people. I prefer a shorter barrel for a quicker moving gun. I do tons of waterfowl hunting and I can reach geese just as far as anyone else with my 24" barrel, if not further. Find a gun that fits you, and get a barrel length that suits your needs best.
In my goose blinds (Final Approach Top Guns), with a dog in the blind I prefer a shorter gun, then again I hardly ever shoot geese beyone 25 yards in the dekes, or ducks. I also shoot alot of sporting clays, and run a pheasant operation and the 24" barrel really shines there as well.
I wouldn't waste my money on a 3.5" shotgun either, thats money you can just buy extra shells with. When shooting steel shot just remember that speed kills. My Benellis' really pattern Kent Fast steel #2s very very well, this is the load I shoot all my pheasants and ducks an geese with. If it gets really windy or nasty out I will switch to BB steel on ducks and geese, but its really not necessary.