ORIGINAL: Rodney
Structural strength is the biggest advantage for airfoiled stabs on models. Since you can make the main spar thicker, you get a stiffer structure which can help in preventing flutter for larger/faster models. For large models, it is usually lighter to have a built up stab as well.
yes- as with most model and full scale airfoils - the primary requirement is that it hold it's shape and not break
after that - all the rest of it is simply shaping it for best efficiency at a given speed and load .