Just one thing to know.... MOSSBERG....
I like the Mossy I own, a M500, for waterfowling. I really prefer it anyway over the 870 I had. The 870 will work, but the express models are rather rust prone. I got mine in camo, really a tough finish. I hunt mostly bays and salt marsh down here and they're really tough on a gun. I've had my 500 for going on 20 years now and it's still shootin' strong and lookin' good, well, a little scratched here and there, but not rusty.
I shoot lefty so I'm biased with the tang safety, though. I can shoot with a crossbolt safety, have that on my Winchester autoloader I'm taking with me this weekend along with my side by side for the opening of dove season, but I really do prefer a tang safety and the Mossberg has that.
If I had the money, I'd buy a Browning BPS in a heartbeat. Well, truth be told, I'd probably get a Mossberg 935 autoloader, but I'd love to have a BPS. As pumps go, that's my top of the line, bestest, most favorite. It combines the SUPER smooth Ithaca action with a tang safety. You won't find a smoother operating pump anywhere in the world. It makes the Remington 870 and Mossberg 500 look like chinese junk by comparison. It's just sorta high for a pump. I can get an auto like the 935 for similar money. I bought a few guns last year so I'm building my gun fund back up. I might go shotgun shopping again in the future and who knows, but I've really been thinking 935 autoloader lately for waterfowl only. I have a 2 3/4" only Winchester autoloader. What I like about autoloaders, gas guns, is the light recoil. That would really help with 3" loads and the 935 will shoot 3.5" also. I might retire the old 500 if I get a 935, but I don't think I'll sell it. I don't like selling guns anymore unless I don't like the gun and I cannot say that about the 500. Besides, everyone needs at least one pump and you can't have too many shotguns.
BTW, I don't know if I'd ever use 3.5" even if I get a 3.5" gun and even on geese. 3" heavy shot is about as effective as it gets, more effective than any 3.5" steel loads. Yeah, the ammo is a might expensive, but you don't shoot THAT much on geese, not like I do on ducks during a season, anyway. You can find 2 3/4" steel that is capable on ducks, much less 3" steel. I don't even know if Canada has steel shot/non-toxic laws, though, but I'm just sayin' I don't need no stinkin' 3.5". I might play with some on geese if I ever get a 3.5" gun, but I don't need that at all for ducks over decoys. The 835 is a good gun, though. If you go that route, get a 24" barrel so it'll balance more like a 500, shorter, lighter action gun. I have a 28" 500, but the extra 4" of barrel is not necessary.