In many cases the advantage is it is legal. It can also be easier to carry in a holster than a slung rifle over the shoulder, especially over rough terrain where both hands free is a blessing. I find any sort of climbing with a slung rifle to be a real pain. My opinion of course, and neither is perfect.
I have to admit the legal advantage had not occurred to me. In my area there is no separate season for handguns, just modern & primitive firearms. (and of course, a bow season).
I'm well aware of the advantages of even a large handgun over a short rifle for carrying, I have scoped 10" and 14" Contender set ups, so yes, I get that.
What got me was the weight. "pushing 9lbs" just seems extreme if not ridiculous to me. As he owner of several magnum semi auto pistols, which run between 4 and 5lbs loaded, I have heard endlessly from some folks about how they are too big and too heavy to be practical, etc., I can see the irony of me saying that about someone else's big pistol.
Seriously if it works for you then its practical enough, right?
A friend of mine I visited today has some personal experience with the Big Horn Armory guns, and says they are extremely well made and worth the price. Also, they hold 6. I believe the big S&W .460 revolver is a 5 shooter??