Although Azdel is apparently a superior product to Luan plywood, I question how much of a benefit it is in laminated wall construction. If you get water intrusion into the sandwich, the only difference between having Azdel or Luan for the outer sub layer is the Luan will absorb water ,and possibly the Luan may delaminate itself. Typically though its the glue that releases from water intrusion 99% of the time, so they can advertise Azdel will not rot, but that does not gain you very much if your wall starts to delaminate. If the fiberglass is releasing from the Azdel or Luan, or Luan or Azdel is releasing from the foam insul, you still have a hell of a problem either way that is almost impossible to repair. At least its almost impossible to repair so that it does not look like a repair. ANother thing they like to put out as a benefit is Azdel supposedly will not have as much telegraphing of seams through the fiberglass. It may not show those as much but I can go on any sales lots and show you where the substrate seams are on either. An RV tech who does a lot of laminated fiberglass body work for insurance claims told me he thinks the Luan is a better choice as the glue adheres better to it. It is more porous than the Azdel. Again, I don't see where it matters much.
R-38 in a trailer roof? They can make that claim but I call BS. R-38 is equal to 12" of fiberglass batt or about 7" to 8" of extruded PS foam. Your not going to get it out of a radiant barrier no matter what the trailer manufacturer or insul manufacturer tells you. They can get it under laboratory conditions but not in your ceiling.
Both look good in the brochure however.