You don't have to store liquid ammonia under high pressure and it has a higher energy density by volume than hydrogen. Also, ammonia is already very useful beyond energy storage, such as for fertilizer. Maybe a hybrid system is the way to go, with hydrogen for smaller consumer applications and ammonia for larger industrial ones. I don't know if there's good way to produce ammonia directly by electrolysis yet, so the ammonia might still have to be derived from hydrogen anyway.