Was there again today. Dashboard is identical to 3 sedan, but front of the car is indeed slightly different with bigger grill and a little higher.
Booth space is really big, but difficult to compare without another 3 aside.
My son did confirm the huge place in the back seats. At least 5cm more than the F11.
He doesn't like the car at all: "you need to be 60 ore more to drive such a car"
There's also an electrical spoiler on the back end and those ventilation on the sides like the 4 coupé.
Sitting in the back, i've 4 cm left above my head (I'm 1,82m).
I would not change my F11 for this car.