Both plus Electric. Diesel engines are built tough and last a long time. Biodiesel runs perfectly in a diesel engine and can be mixed without issue. A conversion can be done to SVO (straight veggie oil). Both of which have renewable challenges, but what doesn't. (Solar, Hydrogen, Natural Gas, Electric, Gasoline, etc.)
Hybrids are great, but the question is what kind of Hybrid? Hybrids have multiple "levels" if you will, some are more green and more hybrid than others.
Fuel economy; or cost to get down the road, is be impacted by a) care for your vehicle, b) driving style, c) speed with which you drive. It's not just the price at the pump or the MPG on the sticker.
We need to consider what want and what we are willing to trade-off to get what we want. Are we only looking for cheap (MPG or the equivalent)? Or are we trying to lower our carbon footprint (green)? Very different solutions. Combustible engines create road runoff that impact our water supplies; just an example of considering the entire transportation question when considering a vehicle. What about the lifetime cost of the vehicle or the lifetime emissions, both from ownership but also manufacturing? When you drive a vehicle off the lot you have also committed X amount of resources to the manufacturing process, some renewable, some not.