I am no expert on brenneke slugs from a 12 ga. I think the 12 ga shotgun represents a more common gun and a gun that is not that hard to master sufficiently for general protection purposes. Kicks hard. Hard. I doubt it has the penertation of the 480/475 and up in the big bore handguns with an appropriate weight bullet for the caliber. But as someone said, you can penertrate the lungs with your 475 or 500 and the bear will die eventually, but it has time to take care of the pesky human who is bugging him/her for whatever reason. Hunting is a different matter
After reading this thread, I think you're better off with 400 gr+ hard cast bullets with the 500 S&W. Factory 350 gr are fairly easy to shoot from a recoil perspective.
I do like the 480/475 caliber. I'd like to own the Alaskan in 480 because I have two other handguns chambered for it. I don't have much need for big bear protection. Never go anywhere other than black bear woods and feel pretty comfortable with the 41 mag if I am actually worried about bear protection (usually I am more likely to have a 22LR revolver with me in the woods).
But if I were heading into big bear woods today, I'd probably take my 41 mag and feel pretty good about it. I would feel the same with a 44 mag with hard cast bullets. But I sure would like to get an Ruger Alaskan in 480 just for the fun of it. I like variety. But I'm a master of none... perhaps 22 revolvers and my 41 mag comes closest to being a pretty capable shooter. But I am not particularly interested in tactical drills and all that stuff.