Is it a plug-in or a self-charging? Plug-in usually has a large battery and a backup petrol engine (not sure if this has a normal capacity tank, but I would expect smaller to make more room for batteries). The self-charging has a normal size petrol tank and uses the petrol engine continually charge a smaller battery to run the car. It gets similar mileage to a diesel but running on normal petrol. The plug-in probably has lower range but cheaper running costs if you are able to charge it and not too dependent on the petrol engine.
You probably have nice cruise control options too :)