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, horsepower, and fuel economy. First of all, there is a notable difference in the starting price of the 2017 BMW M6 Convertible, which is $25,740 less than the base MSRP of the 2017 Maserati GranTurismo Convertible. And finally, although the 2017 M6 Convertible has a more powerful engine than the 2017 GranTurismo Convertible, it gets 1 more mpg. Among similarities are the body structure, market segment, ground shadow size, height, and maximum occupancy.