After driving the 2015 SL for 11,500 miles, I can say that suspension on 2015 is definitely firmer than 2011 SL. Steering feel is also a bit better. Dry grip of 17-inch Michelin Energy tires is slightly better than 16-inch Bridgestone Ecopias, but not as good as Michelin MXM4 replacement tires I had on 2011. Wet grip of Ecopias (when inflated to 44 psi) was equal to or better than both versions of Michelins. Wet grip of Ecopias was really bad at 36 psi. There is not much difference in wet grip with Michelins between 36 and 44 psi. These are personal observations with tire pressures at 44 psi on both cars (except as noted regarding grip)--YMMV. Leather seats in 2015 are also firmer than recycled plastic (cloth) seats in 2011.