I don't think either method has a clear advantage in terms of strength per pound or stiffness per pound. The materials that can be used in foam/glass comprise a wide variety of fibers and core materials so the answer is "it depends". At the high end, using carbon, kevlar, high performance foam and vacuum bagging, the sandwich construction is more efficient.
I have built hulls using both methods and for a home builder I think tortured ply is less hours and less chance of making any serious mistakes. Some people much prefer working with wood opposed to composites because of asthetics and comfort. Lots of opinions on this.

Kevin