The BMW seats hug you front and rear, and are covered in richer-feeling leather. I will say, the Mercedes feels even roomier than the minor dimensional differences would suggest, but the BMW feels more cosseting than confining. Interior materials feel nicer in the BMW, though assembly quality feels higher in the Mercedes.
Comparing wagons to wagons, the Benz is much more practical. The cargo hold is way bigger, the seats fold flatter, there’s a third-row and a real roof rack. No contest.