I love my cheapy 870 Express. I know nothing of the 870 Marine Magnum. Are we talking about something that is basically a short, corrosion-resistant 870 Wingmaster, or a shiny 870 Police, or an overpriced 870 Express?
I gather the 870s are quite different in their internals but I don't know the specifics.
I suppose you can interchange barrels on the 870 Marine, even if you're changing to something in a different finish. Is that right?