My 535 M Sport 2010 it had more of a race car feel to it. The 550, although with more power, it feels rather lager and more like a cruiser. My passengers much prefer my new 550 for its smooth ride. Adding the Integral Active Steering might also contribute to the feeling of the car. The lack of backrest feature on the seats is a great negative point to me. I like to feel the car grounded to the road when I drive. I have not been able to get the same feeling on the 550 yet. The 550i M Sports is a very nice car with a lot of power but sometimes it's not only about how fast you go. It's about the car being an extension of the drive and the experience you feel when you drive it.
The manual mode brings me back some of it.