Two Convertibles with some similarities, but otherwise different in most aspects such as the horsepower, ground shadow size, fuel economy, height, and maximum occupancy. First of all, the 2018 Audi S5 Convertible has a more powerful engine than the 2018 Alfa Romeo 4C Spider, and it gets 5 fewer miles on a gallon of fuel. Also, the 2018 4C Spider body is significantly smaller than the 2018 S5 Convertible, and in addition to that, it's also slightly shorter. And finally, the S5 Convertible seats two more passengers than the 4C Spider. Among similarities are the body structure, market segment, and starting price.