Hydrogen on the other hand doesn't require any rare elements Only when you think that platinum is more commong than lithium. Platinum is used as a catalyst in fuel cells. Lithium is a rather abundand element (comparing to platinum) and much cheaper.

How is it different from liquid natural gas tanks Storing hydrogen is MUCH harder. It requires much lower temperatures (-162C for LNG, -253C for H). LPG can be stored liquefied at room temperature. Natural gas cars use CNG (compressed, not liquefied gas).