Other than a larger internal magazine I don’t see any real benefit over the basic Mossberg 500
Metal trigger group instead of plastic, for one.
A lot less recoil is mentioned. That could be nice for high volume shooting. I find the recoil fine on my standard 500 for how often I actually shoot it though.
My Mossberg 590S cost $299.
So I bought two, plus a case of 00.
The heat shield matters, as does 8+1.
A bunch- already mentioned- Al trigger guard, heavy ( really heavy) barrel- for durability with muzzle attachments and dent resistance ( sporting shotguns are very thin walled and lightweight), Modified safety and beefed up action bars and heavy walled Al receiver etc... NOT a 500.