Two Convertibles, but completely different in all significant aspects: model year, starting price, horsepower, fuel economy, ground shadow size, height, and maximum occupancy. First of all, there is a $98,390 difference in the base MSRP. The 2016 Maserati GranTurismo Convertible, a newer vehicle by three model years, has a higher starting price than the 2013 BMW Z4. Also, the 2016 GranTurismo Convertible has bigger and thirstier engine; the 2013 Z4 gets 7 more mpg. In addition, the Z4 is both significantly smaller and slightly shorter than the GranTurismo Convertible. And finally, there is a difference in the number of passengers; the Maserati GranTurismo Convertible seats two more the BMW Z4. Among similarities are the body structure and market segment.