MO, don't take it so personal, I call them like I see them.
My opinion is based an a couple of things.
First,while some trap shooters,card shooters, and other high volume shotgunners use pumps, the pumps they use are all steel receivers. 870s, Model 12s, and the ancient but superb 97 come to mind.
These folks often own Mossies, but use them for hunting, and a hunting gun sees less shells in a lifetime than a clays gun does in a year.
Second, the 870 is the choice of most agencies ofr the simple reason it holds up under abuse and neglect far better than the other brands.
This isn't opinion, MD DOC's experiment with Winchester 1200s lasted about 3 years, then the 1200s were removed from active duty due to massive malfunctions. Most were traced to dirt and grunge buildup. The 1200 is a very good shotgun when clean.
My 870TB has gone glitchless for 6-7K rounds in the last year. How about firing off an equivalent number through your 590 and get back to us on how it's holding up? Thanks...