What Car? says...
It’s best to think of the Audi A5 as a sleeker-looking but less practical version of the popular A4 saloon – and that's not meant to sound dismissive.
After all, the A4 is a former What Car? Car of the Year so it's a fantastic starting point for Audi to choose. What do you gain by having a higher number in the car's name but fewer doors? Well, that depends which A5 you go for.