No one would care about how loose the forearm is, how much the gun rattles, unless hunting deer or maybe turkey. Me, I have used my 500 for 20 years in the salt marsh and it's held up well, still great! It's my salt marsh duck gun, camo with polymer stocks. I bought a blued and wood 535 which is 3.5" capable, and it feeds 2 3/4" stuff just fine. I have only used it one morning this season dove hunting just to check it out. It is a pretty tight gun and very smooth, but got it used for $170 at a pawn shop a few months back. The 535 is NOT back bored if that matters to you. You might consider it in lieu of the 835 for that reason.
I do not like the 870 and doubt I'd like the 887 for the same reasons, ergos. I shoot lefty and prefer the tang safety and I prefer not to have the shell elevator in the way of loading the magazine. I, too, have heard bad reports on the 887, but take that with a grain of salt as it was on the net and everyone knows how reliable the net is. My choice of the Mossberg is personally biased by ergos and that I shoot lefty.