As a class A owner, and a bus driver who drives a Deisel bus with the super 'C' nose, I really don't think there'll be any difference between the engine being up front with you, (other than the engine noise) or in back, as far as performance. MY biggest issue with my class A, is the fact that theres only one door, and no other way out, except through the window.
When I first purchased my DP, I was driving to the dealer up the NY thruway, to get my punch list taken care of. Looking out the mirror, I saw that one of my basement doors was open. I pulled off to the right, as far off the road as I could, and couldn't get out because of the guardrail. I ended up having to pull off on the left side, exit the vehicle with left lane traffic flying past me, and re enter traffic from the left hand lane....it seems none of the class a's come with driver doors anymore.