BMW F10 5 Series
+ Rear wheel drive = good for bit more sportier and fun driving,
+ Brand = good driving dynamics, although may not be the "ultimate driving machine" anymore
+ Very attractive and muscular looking design
+ Has bit more specialists and parts will be slightly easier to find than Audi
- Very common (specially F10 520D) in roads and thus exclusivity and prestige is somewhat affected.
For 9 million - 2012 520D with low miles.
Pick for enthusiasts - 530D or 528i with M Sport package
Best colors IMHO - Black, havana brown, alpine white
AUDI A6 C7
+ Front wheel drive or AWD (Quattro) - good traction
+ Brand = Young generation's favorite out of German's
+ Very attractive and decent looking design
- It is a premium grade Volkswagen after-all
- Parts and maintenance cost may be slightly higher, specially after warranty period.
For 9 million - 2013 A6
Best colors IMHO - Red, White, Metallic gray
Alternatives - Jaguar XF (2011-2013), Mercedez E Class (2010-2011)
Just my 0.02 cents
Kal-El's post in Audi Vs BMW was marked as the answer