I'd take the 480. I'd be curious to know the general area you intend to travel in. In much of grizzly country the density of grizzly bears is less than one per three hundred square miles, and a weapon is more a matter of insurance with the true likelihood of encountering a grizzly being quite small. In other areas you can expect bear encounters as the norm. If you're heading into an area with a high bear density, I would strongly advise a rifle or better a twelve gauge shotgun.
Once you've been within thirty feet of a brown bear a few times, a rifle or a shotgun no longer feels heavy. In fact the idea of being out of reach of a shotgun or a rifle makes you feel a little sick, but if you do carry a rifle or a shotgun by no means leave the big sixgun. A big sixgun may not be perfect, but it is always there.