If your aim to get from A to B as smooth and quickly as possible, then I back Buck's suggestion and all that he has said.

However, if you have time to enjoy the journey and the weather and road conditions are kind, I personally would consider/prefer the 'other' route along I 70 and down 191 etc. I am not a fan of Interstate travel for pleasure, but they do serve a purpose. The roads [191 etc] are in good shape and offer nothing that a 40ft RV can't handle quite comfortably, the effects of weather would be the same as if you were in a car.