If you could only visit one of the groups that flys SPADS... you will see that:

Early SPAD designs are heavy and not very good. (amazingly like the US Aircores kits...)

Newer SPAD designs can directly compete with balsa models for performance and wing loading. The wings tend to be a little heavier... the fuselages a little ligter than the balsa versions. (A coroplast "copy" of a 4*60 has been made that is the same weight as the kit version by Sig...)

I mostly fly balsa models... I've been building with "oddball" materials every chance I get for over 20 years though. Sailplanes made from refrigerator boxes are interresting and essentially made of free materials.

Balsa was initially used for models because it was CHEAP and easy to get. (you could get it from crates at the grocery store trash pile... kind of like coroplast signs now.) The fact that it is a light strong easilly worked material was just a bonus. If all that had been easilly available in the 1930's was soft pine... we'd be using a lot more soft pine in our models now.

Early use of styrofoam was ridiculed... now its used extensively for wing cores.

Coroplast is just another material to learn to use in order to get the most flying for the lowest cost.