Generally speaking modern hydrogen pressure vessels are not metal for this reason, they are composite and not affected by embrittlement.
The Toyota Mirai, a production hydrogen car, uses a type IV carbon fiber pressure vessel rated for 70 MPa / 10,000 psi.
Type V are rated for 15,000 psi.
It is not necessary to liquefy hydrogen for adequate range in ground transport applications: The Mirai yields a 402 mile EPA rated range on gaseous hydrogen.
The tanks weigh 93kg filled with 5.65kg hydrogen, yielding an approximately 190 kWh of stored energy.
All without corroding flesh in trace concentrations.
By comparison the Tesla Roadster's 450kg battery pack yields a 200 kWh capacity.
Ammonia is and would likely continue to be stored in metal pressure vessels as an obvious cost optimization and thus would compare unfavorably to hydrogen pressure vessels' effective energy density where that area of the performance versus cost optimization space is not available due to embrittlement.
