BMW 8 Series (G14) (2018) is 465 mm (18.31 inch) longer, 102 mm (4.02 inch) wider, 46 mm (1.81 inch) higher and has 188 liters (6.64 ft3) bigger cargo space than Porsche Cayman (2019).
Porsche Cayman (2019) is 518 kg (1,142 lbs) lighter than BMW 8 Series (G14) (2018).