I've test driven the 540i xDrive. Large, refined and luxurious, although the B58 is a bit subdued in that implementation and needs more torque, imo.
My F31 and F36 was/is more entertaining to drive, period.
The 5 is for wafting around in, at a leisurely pace, to my mind. However, if I was looking for something large, refined and luxurious to waft around in, I'd get an E class Merc - no contest, sorry