There is no comparison between a gasoline vs diesel. The diesel is superior on all categories. I have had both and the ride alone is like day and night.
The only way I would go 45'is if I was to go full time. They are long and harder to maneuver in some state parks. I would recommend between 36'to 40'with at least three slides make for a pretty good motorhome.
Diesel coaches because of the engine make them heavy and cross winds hardly bother you. I have a Caterpillar engine and at 38' it weigh's 30K lbs where a gasoline motorhome the same length would probably weigh around 24K lbs.
