I have never heard of anyone posting on this forum that their coach, whether gas powered or diesel, did NOT making it up to the top of any hill or was NOT able to pull their toad, up to the rated capacity of the hitch. This does not mean that all of the various rigs will be the first to the top of the mountain but it means that you will get there, safely, and be able to continue on your journey. I have had diesel and gasoline coaches and the floor plan is still the most important. Fuel mileage should not be an issue if you are looking at a Class A rig. It will not be good, in terms of cost per mile.
If you find a floor plan that you like, don't worry about what engine powers it. If you insist on winning the race to the top of the hill, then open up your wallet and buy a top of the line Prevost class motor home.
