There are two advantages to the MH XLII shell. The longer rear overhang provides a means of getting weight off the front axle by cantilevering the weight of the engine, transmission and whatever other weight the converter can place back there to offset weight that would go to the front axle. The second benefit is the turn radius is better than on the entertainer shell.
With the use of the entertainer shell converters are going to have to work very hard to cut down on weight so the steer axle is not overloaded. I think that is why some converters are going to use the lithium ion batteries. Prevost saves a few bucks by eliminating one model from their lineup but it just transfers the cost to the MH buyer who ultimately pays for the methods used to save weight.
But the turn radius difference is a non issue. As an owner gets accustomed to his turn radius and the pivot point it is doubtful he will wish he had the shorter wheelbase. In all my years of ownership there may have been one or two instances where I was able to make a turn with 0" to spare. Turns are usually relatively easy because there is ample room or they are so lacking it is obvious there is no way to make it. A foot or two difference in turn radius is not likely to make the difference. But what will change is drivers will have to be much more aware of high centering the coach, especially if the conversion has baffles or piping that hangs below the level of the bay doors. That disadvantage will be offset to an extent by a ride that should be slightly improved as a result of the longer wheelbase.