It has a thinner barrel, usually 4 inches from what I have seen, and weighs less, supposedly making it more comfortable for hiking. It is no more suited for hunting than any other revolver of the same caliber.
They are relatively more sought after than standard models, and will cost a little bit more, usually, from what I have seen.
Personally, I would rather have the regular model. The weight savings with the mountain gun is not all that much in terms of hiking, but does make a difference in recoil and shootability. If you are looking for a target pistol, I would buy the heaviest gun out there... with a full underlugged barrel, and leave the mountain guns for people who think they need one.