I've had the opportunity to drive the 428 Grand Coupe M sport for a while my 535D was at the dealer and I have to say it's been a compelling and fun car to drive. The first you notice is the engine noise and throttle response. When you hit the gas the engine screams and the throttle comes to life. You feel like you're in fast machine. However in terms of raw power it doesn't pull quite as well as the 535D. This is the sort of car that makes you want to go full throttle on the gas all the time. In terms of power you have just enough to enjoy going full power all the time without worrying about losing control. By comparison the 535D has more torque but if you're careless you will find yourself sideways fairly easily. The stock tires and steering settings work well especially with the M Sport package. There is plenty of grip in the tires and the steering feels taught and confident. It doesn't feel like there is very much the car can't do. Although I improved my grip on my 535D by discarding the run flats the steering ratio is very fast and it requires a far more precise inputs. This is where the 428 M-Sport really shines it doesn't require very much concentration or precision to get the most of the car's steering, just don't be an idiot driving it. In terms of cockpit space the 428 grand coupe has less real estate than the 535D. However the seats fit nicely and feel sporty. In terms of comfort the 428 grand coupe is quite good, in fact I was able to take a 1 hour nap in the vehicle so I can definitely vouch for the seats. In terms of space it's not a five series and I haven't tried sitting in the back. However from what time I've spent in it I can definitely say that the M-Sport 428 gran coupe is a fun and lively car to drive.