It is not just a matter of power. The big diesel pushers are upgraded in many other ways compared to their gas cousins. The big diesel pushers tend to have better suspensions, bigger fuel, water and waste tanks, and better amenities than the gassers. They ride and handle better as a result of the better long-wheelbase chassis that they are built upon, and tag axles on many of them. Bigger generators and more batteries with big inverters for generator-free operation of electronics without shore power. There is a lot more to consider than just the increase in pulling power.