I have used plywood hive bodies an solid wood side by side. In my opinion
the solid wood is much superior, plywood does not absorb moisture like solid
wood because of the layers of waterproof glue. For wintering they are very
poor because of  condensation. I still have some of them in use for honey
supers or as shells for feeding in the spring or for storage of frames in
the honey house. On the positive side plywood is strong and is dimensionaly
stable and it does last a long time. Mine are 21 years old. Perhaps you
would have better luck with plywood in a warmer climate.

Tony Dixon
Vancouver Island, B.C.
Canada