By all means take them for a test drive, especially if you are looking at used Class A units. Having had both, I know that they will all make it to the top of any hill and they will all get you to your destination. You will spend more time parked so make sure that you can live with EVERYTHING about the floor plan, storage, etc. If you are a DIY mechanic make sure that you are knowledgeable about gas or diesel systems. Engine noise is less on a diesel pusher, but on a used unit, wind noise in the cockpit can be a problem with either. If you have to pay for all service, the diesel will be more expensive and there will be fewer places that can service your engine. Most gas units have the Ford engine and most parts are available at any auto parts stores. Just take any unit you are considering for a ride on a city street and on the highway and see if you are comfortable with everything and that the wife is happy with the floor plan.
Also, If you are planning on towing I think all of the gas units are limited to 5000 pounds, as are some diesels. Many diesels are rated for much more if needed.
