equ's comment turned on a lightbulb.
Before buying my 335is coupe I drove a 2011 335i coupe for comparison. The 335i (N55 engine) was smooth, refined and powerful but it lacked the excitement of the 335is (N54 engine + a mild tune). They were two very different driving experiences.
Driving the 335is on the autobahn revealed the latent "beast" in that vehicle.