Audi S6 (2016) is 34 mm (1.34 inch) longer and 11 mm (0.43 inch) wider than Opel Insignia Grand Sport (2017).
Opel Insignia Grand Sport (2017) is 15 mm (0.59 inch) higher, 530 kg (1,168 lbs) lighter and has 91 liters (3.21 ft3) bigger cargo space than Audi S6 (2016).
