I don't think even 1000 hp in 3x' long coach will be adequate as my 7000lb pickup has 350 hp. ;)
But you don't expect to race BMW with your motorhome like I do with my pickup.
Anyway, I drove diesels exclusively for last 15 years and lately, since diesel wagons are not available in US, I had to buy gasoline wagon.
So last car was the same model of MB Eclass with 174HP diesel. Then newer one has 230HP gasoline engine.
In normal driving gasoline engine feels weaker due to low torque at cruising speed. Where lower HP diesel would make to top of the grade without downshifting, the 30% more powerful gas engine has to downshift.
It comes more clear why if you can compare HP diagrams at cruising speeds, but that is how it works in real life.
