Was watching reviews of these two, same engine and battery but mpg vary by 6-7. Base Ioniq is 50mpg whereas base Niro is 43mpg. The reviewer claimed the same engine. I wonder if just the shape of the vehicle is responsible for this difference. I admit I didn't pay close attention to the weights. Does anyone have more info on this? Not that I am considering these vehicles but lifetime battery guarantee is intriguing.