I have a weakness for the old A5 and all of the clones. If you’re looking for a shotgun to wing shoot with, the right A5 is hard to beat with any pump gun. My favorite is an old Franchi light that I bought in a pawn shop in the late 80’s.
An 870, on the other hand, could easily convert to another purpose with a barrel swap. Security, slug gun or multipurpose hunter. One of my Mossberg 500’s has housed at least 4 different barrels over the years and I still have a custom case that I can pack it all up in.
Bottom line: I bet you won’t be sorry with either of the two.