On nice summer days like those we occasionally get in Michigan, it's almost impossible to tell if a 7-series has an xDrive all-wheel-drive. Despite a 150-pound weight penalty versus the base rear-wheel-drive 750i, the driving experience of the xDrive-equipped car feels almost the same, which is to say, surprisingly sporty for such a large car. The fuel-economy penalty is a bit more noticeable, though, as xDrive makes for a fairly significant hit at the pump, with the EPA fuel-economy rating 1 mpg lower in the city and 2 mpg less on the highway (14/20 mpg city/highway versus the RWD car's 15/22 mpg).
Still, even southern Michigan's winters don't really necessitate all-wheel-drive luxury cars like the 7-series or the 4Matic edition of the Mercedes-Benz S-class (winter tires and rear-wheel drive with stability control are usually sufficient). But in snowier climes, that extra edge can make the difference between getting there and not, particularly if "there" is up your steep driveway. By the way, this is the base xDrive 7-series, as the new six-cylinder 740i/Li will not be offered with all-wheel drive.