For an alaskan guidea rifle is no doubt better,as he may need to put an anchoring shot into a wounded bear getting away. For pure self defense accuracy is a non issue,as the range is likely to be so close it doesn't matter and it's unlikely you'll have a chance to take fine aim.
I feel like the shotguns aren't getting a fair shake here. First off, lets just agree that regular buckshot is less than ideal,so figure it'll be slugs. Lumping all slugs into the same category is really rather ignorant. Soft Foster style slugs are not proven penetrators,and yet have worked on many occasions. Still, I wouldn't pick them as my first choice. Brenneke's and the like are a different critter altogether,and I would feel pretty comfortable with a tube full of those. I know there not easy to get, but I'm pretty sure they are available in a few places in Canada. Most ideal would be the stuff that Dixie puts out, but I don't think it's available in Canada at this time. Maybe one of the dealers here should look into it? Anyway, take a look at some of their loads. This is some serious stuff, basically turning a shotgun into a 12 gauge rifle with big heavy hard cast bullets. Another interesting load they offer is the Tri-Ball load, which is 3 full bore balls,each around 350gr. Testing done at the Linebaugh seminars showed very impressive performance by the Dixie ammo.