Well, for me I've got an Remington 870 express that I carry sometimes - usually when I'm out and about in the boat. I have it loaded with slugs though some will say 00 buck as the first shot to try to slow the bear down for a better shot with the slugs. Others go 00 buck, slug, 00 buck, slug, slug, slug. It's really personal preference.
I think that most would say go with a pump as the autoloader is more susceptible to jamming from dirt, mud, etc. At the distance that most bear encounters happen, sights are not a big issue as most happen within mere yards.
Shotguns are really the gold standard for bear protection. The knock against them is they are rather cumbersome if you are in the willows or alders and they aren't easy to carry while one is fishing. Most of the time I carry a Blackhawk 45 Colt loaded with 365 gn hardcast pushed to about 1050 fps. Also easier to bring into action in a tent.
Hope that helps some.