BMW 3 Series Touring (2018) is 265 mm (10.43 inch) longer, 11 mm (0.43 inch) wider, 136 mm (5.35 inch) higher and has 333 liters (11.76 ft3) bigger cargo space than Porsche Cayman (2015).
Porsche Cayman (2015) is 349 kg (769 lbs) lighter than BMW 3 Series Touring (2018).