Two Sedans with some similarities, but otherwise different in most aspects such as the powertrain, starting price, horsepower, fuel economy, market segment, and height. First of all, the 2015 BMW ALPINA B6 Gran Coupe has bigger and thirstier engine; the 2016 Acura RLX Hybrid gets 11 more mpg. Also, there is a $57,350 difference in the base MSRP. The 2015 ALPINA B6 Gran Coupe has a higher starting price than the 2016 RLX Hybrid. In addition, the roofline of the RLX Hybrid is slightly higher than the ALPINA B6 Gran Coupe's. Among similarities are the body structure, market segment, ground shadow size, and maximum occupancy.