Two Convertibles with some similarities, but otherwise different in most aspects such as the model year, horsepower, ground shadow size, and maximum occupancy. First of all, the 2014 6 Series Convertible produces fewer horsepower than the 2016 SL-Class. Also, the body structure of 6 Series Convertible is slightly larger than that of the SL-Class. In addition, you'll seat two more passengers in the BMW 6 Series Convertible than in the Mercedes-Benz SL-Class. Among similarities are the body structure, market segment, starting price, fuel economy, and height.