Two SUVs with some similarities, but otherwise different in most aspects such as the powertrain, horsepower, fuel economy, ground shadow size, height, and maximum occupancy. First of all, the 2015 BMW X6 has a more powerful engine than the 2016 Mercedes-Benz GL-Class Diesel, and it gets 2 fewer miles on a gallon of fuel. Also, the 2015 X6 body is slightly smaller than the 2016 GL-Class Diesel, and in addition to that, it's also shorter. In addition, you'll seat two more passengers in the GL-Class Diesel than in the X6. Among similarities are the body structure, market segment, and starting price.