I still like fir plywood, but I like 5-ply fir plywood. Less expensive 3-ply plywood in any species of wood is less sturdy than 5-ply.

Composites are far more available, less costly, and will move less in “normal” moisture conditions due to the large amount of non-organic adhesive. Lots of plastic adhesive keeps expansion to a minimum with ambient moisture levels so I agree with what you are hearing. However in real “wetting” or submersion circumstances both plywood and composites expand substantially, I don’t believe composites shrink back to the original dimension as much as plywood after they dry.

I still like plywood better but it will cost a good bit more.

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