With its 2011 redesign the BMW 5-Series is now much more closely related to the 7-Series. It’s smoother, quieter, and–both for better and for worse–has the feel of a larger car. So, why would someone spend roughly $18,000 more for the 7? (Add another $3,900 for the extended wheelbase Li, and another $3,000 for AWD.) To find out, I took a 750Li xDrive for a spin after driving the new 550i.