This includes the hybrid electric vehicle; the purely electric vehicle, much in the news these days thanks to Tesla Motors ; and the hydrogen fuel cell vehicle. They all have their strengths and weaknesses when it comes to various factors, such as cost, convenience, environmental- and human-health impact, and so on. Of course, those strengths and weaknesses are largely quite subjective -- they vary based upon whom you ask, as well as who paid for whatever study is being quoted.

My take is that many of the specifics don't matter that much, and that which type of vehicle should win and which one will win could, perhaps, be two different things.