I think the build quality of current Audi models is superior to that of current MBs. Check out the interior of an A6 or the new A4 and compare with the new C, the present E, the SLK, the CLK, even the S.
As has been stated elsewhere, the interior of the TT (do you get that in the US??) is about the best of any car available today, especially when fitted with the baseball glove leather and stitching.
The detailing for my money is superior, too. Look at the alloy wheels, the rubbing strips along the side, the use of aluminium trim rather than chrome.
Of course, all this could be said of VW, too. How about the new Passat W8? 4 litre 8 cylinder engine arranged in a W format.
1999 SL 500
1993 320 TE
1986 500 SEC