A lot depends on the type of flying you want to do (or are capable of doing).

Coroplast is great if you want to bash your planes around. I think if an all-out nuclear war broke out, only cockroaches and coroplast would survive.

As to foam, there are three types of foam planes, Flat foamies, molded foam fliers, and balsa-covered foam, which is usually reserved for wings only.

Now, that said, Foam wings are heavier than built-up balsa wings, but more resistant to damage.

If your skills are at the point where you are wanting to try a nicer plane than you can build with Coroplast, I would HIGHLY recommend getting a kit. When you build with wood, there are a LOT of things to consider in the design. With a kit, all of the engineering has already been done (Like where to put doublers, and how to strengthen critical areas, etc.)

If you tell us the type of flying you like to do, we can recommend several, well-proven kits.