Azdell has several distinct advantages when compared with the more common Luan/plywood. Azdell is stronger, lighter, with a higher R value and more importantly it will not absorb moisture, ever. It is more expensive than wood and until recently the only manufacturers that utilized it were Lance (in their TC's and TT's) and Nexus.
I toured the Nexus factory last June and saw firsthand how it is installed. The fiberglass outer wall is followed by a layer of Azdell. This is followed by solid foam core and then another layer of Azdell and then the interior wall surface is applied. These are all vacuum bonded (by one very large, expensive piece of machinery), into a strong, lightweight structure.
The use of Azdell is good indication of a quality RV. Eventually it will in all likelihood find its way into more RV's as it is simply a superior way to build.
:C