ORIGINAL: foofydoo
I think alot of it is to so with construction times, Foam is quicker and easier to build. I do not think a foam wing would be any lighter or stronger than professional built built up wing. But the built up wing would probably take four times longer.
I have built foam wings, and built up wings, and have found that foam isn't really that much faster
if the built up is from accurately laser cut parts. Back in the days of die cut kits, getting everything to fit properly
was very time consuming. Cutting a scratch built set of ribs on a band saw? Forget it. Of course the caveat is that the laser cut parts must be very precise, and you need a good jig.
With foam, you still need to cut the core. If it is hand cut, and both sides are not absolutely identical it becomes a real pain. I sheeted 12 sets of wings for a guy one time and the thickness varied by as much as 1/32 inch. If they had been CNC'd, I could have done them in half the time. And you still have to trim and edge glue the sheeting. Glue it and vacuum bag it. Cut out the ailerons, hinge them, cut, etc. servo pockets. I can assemble a good laser cut wood wing almost as fast