Two Convertibles, but completely different in all significant aspects: model year, starting price, horsepower, fuel economy, height, and maximum occupancy. First of all, there is a $28,200 difference in the base MSRP. The 2013 Audi RS 5 Convertible, an older vehicle by three model years, has a higher starting price than the 2016 BMW Z4. Also, the 2013 RS 5 Convertible has bigger and thirstier engine; the 2016 Z4 gets 4.5 more mpg. In addition, the roofline of the RS 5 Convertible is slightly higher than the Z4's. And finally, you'll seat two more passengers in the Audi RS 5 Convertible than in the BMW Z4. Among similarities are the body structure and market segment.