Two Convertibles with some similarities, but otherwise different in most aspects such as the starting price, height, horsepower, fuel economy, ground shadow size, and maximum occupancy. First of all, there is a $27,550 difference in the base MSRP. The 2018 Alfa Romeo 4C Spider has a higher starting price than the 2018 Audi A3 Convertible. Also, although the 2018 4C Spider has a more powerful engine than the 2018 A3 Convertible, it gets 1.5 more mpg. In addition, the 4C Spider is both slightly smaller and significantly shorter than the A3 Convertible. And finally, the Audi A3 Convertible seats two more passengers than the Alfa Romeo 4C Spider. Among similarities are the body structure and market segment.