I suggest that you ask Paul at Sportsmobile, Austin TX your questions about engines, suspensions and drive trains for class b. I found him to be very well informed and he works with all name plates. When one of us owners answers we may be biased in favor of whatever we drive.
I drive a 2004 Sportsmobile/Sprinter2500 with 240,000 miles. The original quality was better than the Coachmen that I formerly drove but I haven't evaluated other brands. The I5 diesel continues to be efficient and powerful enough for the job. I don't intend to get a new b but if I did I would certainly consider the new 4 cylinder Sprinter diesel.