Two Convertibles with more similarities, such as the body structure, market segment, ground shadow size, height, and maximum occupancy, than differences, like the modifications, starting price, horsepower, and fuel economy. First of all, there is a notable difference in the starting price of the 2018 BMW M6, which is $142,000 less than the base MSRP of the 2018 Bentley Continental GT Speed. Also, the 2018 Continental GT Speed has a more powerful engine and gets 2 mpg less than the 2018 M6. Among similarities are the body structure, market segment, ground shadow size, height, and maximum occupancy.