How is that efficiency calculated, respectively?
I believe all Hydrogen vehicles are using proton exchange membranes still, which have roughly 40-50% efficiency.
And that's before you take into account that even the most cutting edge hydrogen refining processes are around 70% efficient.
So 1kWh of energy input (electricity) will net you 3X the motive power when used directly in a BEV than first being coverted to hydrogen, and then converted back into electricity.[1]
[1] 0.5*0.7 = 0.35.
And that’s before we get to the fuel costs - £90 to go 400 miles in a Mirai, versus £5.50 to go 300 in an EV6.
Proton exchange membranes are very unreliable and expensive. They are also not power-dense, one that powers a bus will be very large.