For defense, a shotgun is the best choice. But, this is a hunting forum and not many people are going to hunt deer (or whatever) in grizzly country with a shotgun.

The reason I like shotguns (for defense, not hunting) is that actual attacks happen lightning fast. Shotguns are designed for that type of shooting - point and shoot. I mean, if you can swing up a shotgun and kill a pheasant that rockets off at your feet, then you have a reasonable chance of swinging up a shotgun and delivering a slug to a bears face.

And forget all that business about "bullets bounce off a bears head". That's a myth. A bears brain is actually behind the nose and mouth. Grizzlies have a "forehead", but behind that forehead is nothing but a bony ridge which provides muscle attachments for the powerful jaws. The brain is actually behind the nose and mouth. A forehead shot will just make a grizzly angry, and that's where the myth originates.