I think there's a risk of "it's too soon to say here" when deciding on fuel vs battery Vs hydrogen. The problem is that this is a highly complex dynamic system with different people experiencing different externalities.

Reasons answering this question is difficult are, for example:

- given the demands for highly valuable electricity and alternative use cases, why do we insist on using it in locomotion?

- given marginal electricity pricing, everyone is subsidising cleaner air in cities for the benefit of air quality of only those living in cities

- might electric buses be prevalent because of smaller up front costs to infrastructure, and not because it's the right thing longer term?

- if electrification of transport in general was a bad idea (first bullet) then how does this change the economics of hydrogen given the longer run access to SMR sourced hydrogen from longer term fossil fuel extraction?

- how sure are we that we are solving a co2 climate crisis with the actions we are taking?

This all in the context of "greening" our economies when all the dirty industry and carbon emissions are exported to China, out of sight but not out of the true equation. And then there's the destruction of industrial capacity in Europe carried out by green agendas, all in favour of the Chinese Communist Party longer term.

I think this "debate" is largely irrelevant: China has decided that locomotion will be (battery) electric. That is the largest scale you can get, so any effects of scale for an alternative will at best be as large as the battery electric one.

And then there are the variety of other disadvantages that come with hydrogen: - significant leakage and high greenhouse factor - heavy support equipment need (both for storage and for usage)

About the only advantage of hydrogen (vs. lithium-ion batteries) is gravimetric energy density (where it's about a factor of 300). But even volumetric energy density differs only be a factor of 5-10. (Both numbers ignore that the storage thing will add significant weight). And those are _already_ not limiting for locomotion needs.

- how sure are we that we are solving a co2 climate crisis with the actions we are taking?

The thing here is yes: Even if we would generate the energy for the locomotion completely with fossil fuel! Large plants are significantly more efficient (10-35% vs up to 60%) and it would be _much_ simpler to, e.g. think about carbon capture if we had tens of thousand CO2 emitters rather than a billion. But we are not doing that!