BMW 4 Series (2020) is 376 mm (14.80 inch) longer, 51 mm (2.01 inch) wider, 88 mm (3.46 inch) higher and has 290 liters (10.24 ft3) bigger cargo space than Porsche 718 Cayman (2017).
Porsche 718 Cayman (2017) is 159 kg (351 lbs) lighter than BMW 4 Series (2020).