My current 500 has been shooting ducks for 20 years. I just wanted the camo finish. It's far more rust resistant than a Remington Express. I had a Revelation M310 that was fine, had bought a 500 barrel, accu-choke for it and used it for 10 years after the steel shot law passed. Sorta wish I'd kept it, but it was redundant.
My 500 has been dunked in salt water, mudded, been through heck and back. It always cleans up nice, no rust to date. I got nothin' but praise for it as a duck gun. Sure, i'd rather have a BPS, I guess, not sure why. The Mossy does the job. Back before tungsten got so expensive, it was also my goose gun. I've got a 10 gauge for that, now. It reaches out there on those blue bird days with steel T shot.
See, you don't buy 1500 dollar guns to toss in the salt and mud. I trip over something or the mud sucks my waders down and I trip at least twice a season and the gun goes where it goes when I'm falling, LOL. I don't often go on those private land hunts where you're driven up to a blind. It's wade/walk in the muck and salt grass up to a mile and hide in the Spartina grass. There are a few spots where I can use a kayak. I ruined a nice Spanish made double inside 10 years doing this. Oh, it still shoots fine, just ain't so pretty anymore. I wouldn't wanna do that to a Cynergy or something. YMMV