BMW 8 Series (G15) (2018) is 451 mm (17.76 inch) longer, 101 mm (3.98 inch) wider, 46 mm (1.81 inch) higher and has 270 liters (9.53 ft3) bigger cargo space than Porsche 718 Cayman (2017).
Porsche 718 Cayman (2017) is 483 kg (1,065 lbs) lighter than BMW 8 Series (G15) (2018).