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.
By comparison the Tesla Roadster's 450kg battery pack yields a 200 kWh capacity.
All without corroding flesh in trace concentrations.
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.
It poses an immediate danger to life and health at concentrations below the lower explosive limit of hydrogen.
Not every hydrogen leak is a concern, but just about every ammonia leak is.
The established OSHA 15 minute exposure limit for ammonia is 35 ppm, 8 hours is 25 ppm.