I am not an expert in this field, but I would say definitively fuel cars.
During the combustion of diesel and fuel in general, lots of CO2 molecules are free into the air. Those are the main responsible for the greenhouse effect in our atmosphere.
Electric cars do not release, or very little, those CO2 molecules.
I do not know if my colleagues can give you a better answer.
Roborto is correct 🙂 When just looking at running the cars, fuel cars involve burning of the fuel which releases lots of carbon dioxide into the atmosphere and this can contribute to the greenhouse effect 🙂
To make these cars however the fuel car is actually less harmful to the environment than the electric car as there is a lot more ( sometimes almost 70 percent higher) emissions that are associated with global warming 🙂
These extra emissions are made up for after about 18 months of driving the car as the electric car is far greener to run 🙂