I think hydrogen will win out -- eventually. The problems with hydrogen are that it's only in a liquid state at extremely cold temperatures or extremely high pressure (neither are viable options - so that rules out liquid hydrogen). This would seemingly leave us with the option of using compressed cylinders of hydrogen gas. But hydrogen is also the smallest atom on the periodic table -- which means if there's the slightest flaw in a seal then it would probably leak.

This makes refueling and the fuel distribution logistics more of a problem that it was for petroleum fuels.

Somewhat recently there was a breakthrough in hydrogen storage which binds hydrogen to a pellet. The pellet is completely safe to handle and can be stored at room temperature and no hydrogen loss will occur until the pellet is exposed to a catalyst to release it's hydrogen. A citation from a related article that I can no longer find said the pellets exceed current US Dept. of Energy reqts for 2015 by providing enough energy for a car to drive 500km on 50 liters of fuel. (You can see a press release at: http://www.investindk.com/visNyhed.asp?artikelID=13655 )

That sounds fairly promising because it looks like it overcomes some key problems with hydrogen fuel.

The part I don't understand is what they expect to become of the salt from the pellets. If you read the short article, it basically explains that they use sea salt to bind amonia. The amonia is catalyitcly made binding nitrogen to hydrogen. Ok, fair enough. But if you then expose the pellets to the catalyst to release the hydrogen, the nitrogen can just go back into the atmosphere, leaving you with the original sea salt -- but what happens to all that salt? Is it recycled to make more hydrogen pellets? This would mean the car would have to have a holding tank for the spent salt pellets. Environmentally it would be a bad idea to just dump the salt onto the roadway as the pellets are consumed. Salt tends to accelerate corrosion of metals, sours soil to the point that vegetation wont grow in salty soil, and storm drain runoff could be a problem for freshwater rivers and lakes.

I'm inferring that a vehicle would need a holding tank for spent salt pellets. The salt would either need to be recycled into new hydrogen fuel pellets or the salt would need to be disposed of in a way that doesn't harm the environment.

Still... it's a progress and looks to have promise.