[Macias]

Both cars are great in some ways, but quiet different. I've tested M8 Competition Gran Coupe, because my dealer didn't have M850i.

I was considering the M850i Gran Coupe or the M550i. In the end, I chose the M550i.

Why? Because the M850i compared to the M550i:
- has a smaller trunk
- there is no massage option for the front seats (wtf?)
- there is no auxiliary/parking heating option (Webasto)
- there is no Ambient Air
- there is no additional 12V socket in the trunk (e.g. for a travel fridge)
- the rear center seat is practically non-existent, so you have a car for 4 people
- there is no height adjustment of the headrests on the back seats
- it's heavier and you really feel it's heavy
- the Bowers&Wilkins sound system sounds worse
- costs 40k EUR more (with similar specs)

The M550i seems to be more versatile and can be better equipped. In the M850i, the driver sits a little lower, and the overall impression of the car is sportier. The M850i has better soundproofing (acoustic glasses), and the rear side blinds in the doors are electrically operated.

The rest is very comparable, so it's a matter of taste or priorities.