Two SUVs with some similarities, but otherwise different in most aspects such as the model year, horsepower, fuel economy, and height. First of all, the 2016 QX50 has bigger and thirstier engine; the 2013 RDX gets 2.5 more mpg. Also, the RDX is slightly taller than the QX50. Among similarities are the body structure, market segment, starting price, ground shadow size, and maximum occupancy.