BMW 8 Series (G15) (2018) is 465 mm (18.31 inch) longer, 102 mm (4.02 inch) wider, 48 mm (1.89 inch) higher and has 258 liters (9.11 ft3) bigger cargo space than Porsche Cayman (2018).
Porsche Cayman (2018) is 519 kg (1,144 lbs) lighter than BMW 8 Series (G15) (2018).