I have owned both and either would make for a great gun.
I loaned out my 835 to a friend and he loved it so I decided to buy a new shotgun to go deer hunting in Wisconsin a few weeks ago. When I started shopping I was looking for a 835 and thats what I got. Many people shoot the 870 because that was dads shotgun and it is reliable.
Id say my 835 patterns better and in the case you ever decide to expand the shotguns use... Id put the MB rifled barrel against any on the market for slug barrel accuracy.
That said, both are excellent guns.
PS- when I was shopping around, I found several used 835's in pawn and gun shops in Western WA for under 250$ Brand new at walmart in Camo its 309$... you wont get the Rem for that!