The 870 is modular, cheap, and tough
It depends on which 870 you are looking at. If you are holding one of the new 870 Express models then I'd agree with you 100%. They look like crap and have a nasty habit of surface rust.
On the other hand, if you are holding the Wingmaster I'd disagree. They really should have been given different model numbers because I just don't see them being anything close to the same gun.