If you plan to tow 10K lbs or more, then you might want to consider a DP...otherwise, the gasser will be just fine. Your main limiting factor for towing on the majority of Class A coaches is going to be the capacity of the hitch that's installed. And that can easily be changed.
And honestly, does it matter how fast you get to the top of the hill as long as you get there? Like someone above said, find a floor plan you like and go for it!!! Good Luck!!
**EDIT** - Oh, and you won't be able to brag to everyone about how much money you spent on your coach... LOL! J/K with you diesel guys...I'm just jealous...... :B