Hydrogen vs. Battery Electric Cars

Two things you didn't touch on, which I think is a big deal: 1) what is the energy density between the battery vs hydrogen after compensating for efficiency. The density is so different even with the efficiency losses the fuel cell is still better 2) why was there no discussion on the environmental impact between hydrogen and batteries? The batteries are really bad to produce, all the special materials are really bad. But hydrogen is just breaking down water. That's it, there's no mining of goofy metals or anything like that.
This was a good series in that it shines a light on fuel cells, but I think there were a couple key things that got missed.