Not a bad review a few things I noticed though. That 870 was not a parkerized 870. It was a standard matte finish. Also the reviewer pointed out that the Mossbergs come drilled and tapped from the factory and while this is true, Remington has also recently started drilling and tapping their receivers from the factory as well. Remington has already started this pactice with their "Tactical" line of shotguns and from what I understand will start doing this to all of their Police and HD guns as well starting next year.
Hick14454, capacity should never be an issue with a shotgun since you should never be running it dry. Maintaining continuity of fire is important. With the proper tactics, training and equipment your shotgun will never really go "empty". So those extra one or two rounds you get with the 590, depending on what model 870 you are using, is not going to make that much of a difference.