Two Convertibles with some similarities, but otherwise different in most aspects such as the modifications, horsepower, fuel economy, ground shadow size, height, starting price, and maximum occupancy. First of all, there is a $15,600 difference in the base MSRP. The 2018 Mercedes-Benz C-Class Convertible AMG C 63 S has a higher starting price than the 2018 Alfa Romeo 4C Spider. Also, the 2018 C-Class Convertible AMG C 63 S has a more powerful engine than the 2018 4C Spider, and it gets 9 fewer miles on a gallon of fuel. In addition, the 4C Spider body is significantly smaller than the C-Class Convertible AMG C 63 S, and in addition to that, it's also shorter. And then, you'll seat two more passengers in the Mercedes-Benz C-Class Convertible AMG C 63 S than in the Alfa Romeo 4C Spider. Among similarities are the body structure and market segment.