If you think about it a golf ball is spinning so the textured surface (dimples) present an equal roughness no matter which way it sees the air. A hydroplane with mini steps is only going in one direction so the texture can be refined for a unidirectional flow. As Nony says there is not much of the boat in the water anyway.
I still cast my vote with the textured surface. If we had the patience to create the mini steps that would be best but secondly, and not far behind, is a random texture.
Peter