Two Convertibles with more similarities, such as the body structure, market segment, starting price, fuel economy, and height, than differences, like the horsepower, ground shadow size, and maximum occupancy. First of all, the 2015 BMW 6 Series Convertible produces fewer horsepower than the 2016 Mercedes-Benz SL-Class. Also, the 2015 6 Series Convertible has a slightly larger body than the 2016 SL-Class. And finally, you'll seat two more passengers in the 6 Series Convertible than in the SL-Class. Among similarities are the body structure, market segment, starting price, fuel economy, and height.