The main difference between plywood and thin sheets of solid wood is that in the plywood the grain doesn't all run in the same direction. The plywood also has layers of glue running throughout it.

For a given thickness the plywood is probably stronger and stiffer. For a S&G hull the plywood will also tend to hold the fairness of the shape better than very thin solid wood.

The direction you seem to be going in is a cold-molded solution, in which you would be making up your own plywood out of thin veneers, right on the molds, and in the shape, of your boat. This would require a set of forms more like a strip-build boat than a S&G boat.