The test vehicles usually have all the bells and whistles. and rental cars usually have none of those, just a barebones car. so both experiences have their upsides. 3 series is a great car, but feels crappy and cheap inside in the lowest trims ( at least here in Europe).
imo these cars have nothing in common except may be price. i’d go for the cayenne as i am not a 50 yo executive with a dedicated driver. ( thats my steriotype for a 7 series owner-sorry).