Real.....In your price range, you can buy a fairly new gas motor home versus a much older diesel. Any modern gas coach will climb and descend well in the mountains. TYPICALLY, the majority of gas motor homes come with more sleeping options.
When offroading, even on flat dirt roads, a diesel can cause quite a storm. They draw their air from underneath (rear radiator diesels - more in your price range) and blow it over the engine, through the radiator and change air cooler and out the back of the coach. Running one in the dirt will require more maintenance to keep the cooling system clean.
In your price range, your best bet will probably be a gas coach. Buying a diesel in your price range will be much older and most likely need much more expensive maintenance to keep it running.