Hydrogen vs. Battery Electric Cars

As long as you don't take the hydrogen in ultralight balloons with you, you have to count in the weight of the tanks, which are many times heavier than the hydrogen itself.
Counting in the tank weight and the efficiency of the fuel cells, you get a "practical" energy density of ~850 Wh (electricity) per kg for hydrogen. With the carbon fiber enforced tanks used in today's fuel cell cars.
Still much better than today's batteries, but not in a completely different scale.
But you also have to count in the weight of fuel cells and auxiliary aggregates (air compressor, buffer battery,...), which you don't need for battery electric propulsion.