BMW 6 Series Gran Turismo (2018) is 712 mm (28.03 inch) longer, 102 mm (4.02 inch) wider, 246 mm (9.69 inch) higher and has 447 liters (15.79 ft3) bigger cargo space than Porsche Cayman (2019).
Porsche Cayman (2019) is 390 kg (860 lbs) lighter than BMW 6 Series Gran Turismo (2018).