Diesel engines are way tougher to maintain generally needs to be by specialized heavy diesel mechanics. They also need more frequent overhaul over the service life. For regional passenger moves and short haul, battery trains are more viable than hydrogen in the medium to long term. Hydrogen requires specialized containment and a lot of specialized infrastructure. For long haul freight (> 100km), hydrogen could be viable possibly, but electricity is still much lower opex that would offset the higher capex.