Two Convertibles with more similarities, such as the body structure, market segment, ground shadow size, height, and maximum occupancy, than differences, like the starting price, fuel economy, and horsepower. First of all, there is a notable difference in the starting price of the 2016 BMW 6 Series Convertible, which is $60,940 less than the base MSRP of the 2016 Maserati GranTurismo Convertible. And finally, the 2016 GranTurismo Convertible has a more powerful engine than the 2016 6 Series Convertible, and it gets 5.3 fewer miles on a gallon of fuel. Among similarities are the body structure, market segment, ground shadow size, height, and maximum occupancy.