Two Convertibles with more similarities, such as the body structure, market segment, fuel economy, ground shadow size, height, and maximum occupancy, than differences, like the modifications, starting price, and horsepower. First of all, there is a notable difference in the starting price of the 2016 BMW Z4, which is $21,150 less than the base MSRP of the 2015 Mercedes-Benz SLK-Class SLK 55 AMG. Also, the 2015 SLK-Class SLK 55 AMG has a more powerful engine than the 2016 Z4. Among similarities are the body structure, market segment, fuel economy, ground shadow size, height, and maximum occupancy.