The problem is that hydrogen has radically improved in the last decade, but batteries have not overcome it’s fundamental weaknesses. For instance, we are now see hydrogen drop to below $2/kg even with entirely green hydrogen. Fuel cells have also gotten cheaper and more reliable.

The efficiency argument might end up being the same argument made against ray-tracing in the 3D rendering world. In that instance, the upside of have correct lighting with a simple algorithm eliminated whatever upside you could get out of a faster but more complex rasterization system. Hydrogen could easily be the way to have a single simple technology that works in all transportation cases.