The only design aspect of the 4 I like over the 6 is the headlights. The 6 has ugly headlights. Other than that the 6 is much more beautiful.
2014 BMW ///M5 Individual Frozen Grey, Silverstone Full Merino, Piano Black, Exec Pkg, Drivers assistance plus, LED Pkg, Bang and Olufsen, 20" 343M Forged Alloy Wheels
Countermeasures: Bel StiR+, Laser Interceptor Quad HP, Zaon MRX
Upgrades: Eisenmann Sport with M Performance Carbon tips, Dinan anti-roll bars
2015 Jaguar F-Type R Coupe