The way we use plywood to make frames is not at all what plywood was invented for. I doubt there is any real testing done on it for how we use it. This being said, we know it can work well. I would think when it comes to resisting the forces to collapse a frame, the Baltic Birch is stronger than Okoume for any given thickness, it is also heavier. But if I wanted to torture plywood into the shape of a boat, nothing comes close to BS 1088 Okoume plywood. This is a lot like the strip canoes people build, always looking for a way to make them lighter.
At what point is lighter not better than the strength sacrificed?