I've never owned a gasser but rented a new class C, 31 ft, one slide unit in 2004. It seemed fine for what it was, plenty of power, easy to drive.
I knew when it was time to purchase, I've heard it said several times to 'buy your 3rd motorhome first'. We rented two 38ft. Fleetwood Expeditions...a new 2005 and then a new 2006. That gave a us a good perspective of what we 'thought' we might want.
We knew we wanted bigger than 38 feet and ordered our current coach which 42.2 ft. long. I wanted plenty of CCC so that's why I wanted a tag axle.
At just over 40,000 lbs and pulling a 3,400 lb. toad and with our 425 hp Cummins, we go slow up steep grades. I'm sure there are gassers that pass us, we just wave and continue up the hill. We have averaged about 7.3 mpg's over 62,500 miles and we have made it over every hill! LOL!
There is nothing wrong with gas units but I wanted all the creature comforts that you find in heavier coaches which tend to be diesels (corian counters, full tile floor, washer and dryer, full size residential fridge, dishwasher, king bed, plenty of pass-through storage and air brakes with an engine brake) We also wanted unlimited hot water (Aqua-Hot system). So, as you can see, it was a diesel coach or nothing.
As they say, the sunrise looks exactly the same from a pop-up camper to a $2M Prevost. Buy what fits your needs.
MM.