I happen to have liked parts of the old rhino better. It had a more cartoony style that better fit in. For instances the eyes, the horns, and the mouth. I think more use of the darker shade (like in the updated version) should definitely be applied. The Volcano should be as in the newer one, but with slightly paler colors.
I think it should be a combination of the two.
Other then that, I'm loving this style and animations.