2016 Cadillac ATS Coupe is the newer version with some differences, such as the horsepower and fuel economy.. And finally, the 2016 Cadillac ATS Coupe has a more powerful engine than the 2015 Cadillac ATS Coupe, but it gets 1.7 more miles on a gallon of fuel. Among similarities are the body structure, market segment, starting price, ground shadow size, height, and maximum occupancy.