Class A diesel is very quiet, at least mine is. We've had gas for about 40 years and the diesel make a great deal of difference. Quieter, smoother ride. But it is really all about the floor plan, and in the past, for many reasons, the Class A had the best floorplan for our family's needs. One thought about a Class C. Sit in the cab and then maneuver out of both seats and walk to the back. Now think about doing this procedure after driving for 2 hours and wanting to stop for a rest. At my age, with my back and knees I cannot easily get out of the cab and exit into the coach.
Best to you and yours, and Happy Trails.