BMW 5 Series (2014) is 621 mm (24.45 inch) longer, 100 mm (3.94 inch) wider, 267 mm (10.51 inch) higher and has 277 liters (9.78 ft3) bigger cargo space than Porsche Cayman (2015).
Porsche Cayman (2015) is 395 kg (871 lbs) lighter than BMW 5 Series (2014).