BMW 3 Series Gran Turismo (2021) is 448 mm (17.64 inch) longer, 29 mm (1.14 inch) wider, 216 mm (8.50 inch) higher and has 359 liters (12.68 ft3) bigger cargo space than Porsche Cayman (2018).
Porsche Cayman (2018) is 175 kg (386 lbs) lighter than BMW 3 Series Gran Turismo (2021).