What we have here are two Coupes from BMW with some differences, such as the model year, horsepower, and fuel economy. First of all, the is a newer vehicle by 3 model years. And finally, the 2013 3 Series Coupe has a more powerful engine than the 2016 4 Series Coupe, and it gets 3.8 fewer miles on a gallon of fuel. Among similarities are the body structure, market segment, starting price, ground shadow size, height, and maximum occupancy.