Small Electric Aircraft are best suited for Foam in thier design. If you want to fly any fuel or gas Aircraft, In my opinion I would stick with balsa Wood construction. It is much more sturdy for larger engines. Foam wings on fuel aircraft , have a Balsa wood exterior, which sheets the entire wing for added rigidity and strength. You , in just learning the basics would be fine with either, foam or Balsa Constuction for a Trainer.