There is no real life answer to the OP's question. One cannot compare cars based on power/fuel economy. To elaborate, you can have a 18 year old kid and an 80 year old grandmother behind the wheel of the same car and have two completely different results due to driving habits.

The only way to find an answer to this question is to put the car(s) on a dyno and datalog both power and fuel usage rate. By comparing the fuel usage rate at peak power you can get a snap shot of "best power/fuel consumption", not overall.