Audis are repackaged VWs sold at a premium price. Might es well buy a Škoda - they're repackaged VWs sold at a budget price.
BMWs are for arrogant pricks.
Real men drive Audis.
Yeah, that and...
"Thinking is for wussies! Students are pussies!"
That's quite a feat, seeing as how Audi has been around longer than VW. Arguably it is in fact the opposite situation. VWs of late seem to be taking after Audis. The Passat in particular.
Audi is part of the VW corporate conglomerate. They use identical platforms across several car models and bascially just change motors, suspension, coatwork, interior design and such.
IIRC, the A6 is based on the VW Passat, The A3 and TT are based on the VW Golf. The A2 is a pimped-up VW Polo.
AFAIK Audi has always made their own chassis' so if there is any platform sharing going on here it would be the other way around.