Internal combuction engines jsut arnt worth it as ways of generating electricity, so all current on the market hybreds are more trouble than they are worth.
The mini-turbines in the jag concept hybred are far better I beleive, they are just expensive, but said jag beats the prius on most performance indicators, speed, acclleration, fuel efficiency (as in millage per unit of fuel) CO2 output, It also will run on most commercially acaliable fuels, including LPG, Petrol, diesal, Bioethonol etc. It is howver bloody expensive.
The fuel cell is basically a battery, that can be topped up many times. While it does put out water vapour, a green house gas, this is countered by the fact, its easy to condense water and therefore limit its emmission, also the easiest way to make it is by applying electricity to water, so if you have a clean reliable source of elctricity, then you have a very clean system.
However to all intents and purposes it is estially a very dangerous battery tech. so if a non toxic, compact battery could be made then surely that is better.
Electricity if it can be got to a vheicle is a useful power source, and a mechanically simple, but high performance vheicle can easially be made.