Since vehicles are pretty safe already, I would choose green. As in, high fuel efficiency and minimized toxic emissions. I wouldn't want to have a car that used that ethanol-hybrid gasoline that comes from corn, though, because that would just increase food prices due to more corn being used for car fuel instead of food. Hydrogen fuel cells might be pretty efficient, but I'm pretty certain they still have years to go before being as overall efficient as gasoline. But "green" in general.