My opinion is you don't need to waist money on a Rifled barrel. With my $169 Walmart 12 gauge. Smooth barrel. I can hit paper at 100 yards w no scope with rifled slugs. I have no opinion between the 500 and 870.
On the Rimfire. I like the 10/22. Very versatile. But if you can put 22 Magnums in the bolt action then it's a hard choice. But if you can't use Mags then the 10/22 hands down.