I would be happy to own either an 870 or a 500/590. Here is some information to consider from AimPro Tactical website:
"There are many differences between Mossberg® pump action shotguns and other brands, some of the most notable are: Mossberg® receivers are aluminum alloy, other brands are usually steel. This makes the Mossberg lighter and easier to work on. (more on that later) Mossberg® 500/590 series shotguns have dual extractors, the competitors only have one. Twice the extraction power,means more reliable extraction. Mossberg® 500/590 series shotguns have an ambidextrous safety located on the top rear of the receiver. Right or left handed, strong or weak handed, the safety is always operated the same way. Other shotguns have cross-bolt safeties, OK for a right handed shooter pushing the safety off, but after that it means leaving the shooting grip every time you need to manipulate the cross-bolt safety. Not so with the Mossberg® ambidextrous safety, just grip the shotgun and you’re good to go, without ever changing your grip. Mossberg® 500/590 series shotguns have the Action Lock Lever, (other brands call it a “slide release”) at the rear of the trigger guard. This makes it ambidextrous also. The other guys’ “slide release” is at the front of the trigger guard, which means with theirs, you have to leave your shooting grip to get to it."
and I believe the 590 is the only pump shotgun to have ever passed military testing. According to AimPro Tactical:
"How did it pass the Military testing if its' receiver is alloy? The secret to passing the 3000 rounds of high base buck shot reliability test is in the steel-on-steel lock-up of the full square cut Mossberg® bolt lock. Unlike other shotguns, which use an angled shoulder type bolt lock, the Mossberg® bolt lock is a completely through the barrel bolt locking system. The square cut bolt lock is captured in a square cut-out in the barrel, so at the time of firing, the strength of the steel-on steel lock-up is unsurpassed. Add the exclusive dual extractors for positive extraction and you have the answer to who makes the most durable and reliable fighting shotgun."