Porsche Cayman versus Boxster
For the updated Boxster and Cayman models Porsche gave both a new numerical moniker, 718, making them miserableness. Both sports cars have always used the same chassis, but Cayman comes in a coupe form and its older brother, Boxster, as a roadster.
Both share the same engines, interior parts, and even front and rear ends. Practically, the only difference is with the design of the roof. And of course there are performance differences even with the same engines, because of the difference in structure and weight of the body.