I don't know if this will be much help but the roofline of the 850 has always seemed lower to me than that of the 940 and before that the 7xx models.
It's possible the seat is mounted lower in the car so that headroom would be the same between the two cars which might be another consideration for you.
Although i'm not that tall i sometimes find the seats are a bit low to get into so could be worth checking out as well.
