The drive train is obviously a different issue Moreover, if we could have lighter batteries, the lighter hybrid or all electric would be even more efficient.

The drive train is obviously a different issue Moreover, if we could have lighter batteries, the lighter hybrid or all electric would be even more efficient. How many hybrids/electics do you see being made with lead-acid batteries (extremely reliable, proven, safe), vs Li-Ion? Basically none. Because the weight is so much of an issue that it makes them impractical. Just because one factor (hybrid or electric drive train) can compensate for another factor (weight), does not make that factor irrelevant.