Bruce-

First off, I am *not* about to say what I do herein because my RS6 is listed for sale. I want the new S6 and going after the v-10.

Bottomline: I have precisely the same affliction (MB and Audi) for my daily driver.

Ultimately, they're both great high speed cruisers. The Audi is a much better athelete though. So do you want just ultimate speed? if so...MB. You want a friggin 4 door sportscar that has you using the word "friggin" to enhance your enthusiasm? RS6

Or just do like I do (which it seems you already have): remain indecisive and flip back and forth between the two marques.

But rest assured that after you drive an RS6 fast, you should have an easy choice. The car is so quick and surefooted.