There are indeed pros and cons to each type. Wood is an insulator, whereas aluminum tube can have spaces that are not. Bat insulation can settle (if installed poorly) and block foam can be an advantage. Like was stated, aluminum vs wood regarding the roof is a non issue. Jayco's magnum truss is wood and is almost the gold standard in weight strength. But parallel arched aluminum is pretty good also. Stick and tin trailers are the best value per dollar and are very easy and cost effective to repair. Aluminum and fiberglass units cost more per foot to build and can be very expensive to repair. Fiberglass sided units have less drag when towing and thus are generally less fuel consuming compared to stick and tin units. Some of the best made high end models, primarily 5th wheel units, that are definitely cold chambered and rated have wood floors and roofs.
There really is no "perfect" trailer construction. It all depends upon the way it will be used, the amount one has to lay out to purchase, the actual materials and attention to detail, etc.
