This is like the classic Ford vs Chevy debate, you will find something around a 50/50 split given big enough pooling sample. Neither the 870 or the 500 / 590 are the best of choices for the clay sports, both can work for hunting, as to how well it depends on the type of hunting. On the barrel topic, barrels can be changed out in less than a minute, and cost about half the price of a cheap shotgun model. Also keep in mind there are 2 quality ranges on the 870, the cheaper 870 Express that was introduced in the 90's and the higher end 870 Wingmaster that has been around since the 1950's or 60's.
Ike
p.s. the Police model 870's are the same as the Wingmaster, but usually with a dull finish, this should not be confused with the new "Tactical" model which is an 870 Express