I find it quite amusing all the "Lexus is unreliabel" etc claims...
Audi is the one that has become "bland" over the years.
In this case, I would choose the Lexus. For what the A8 represents and costs, it should be a lot more special appearing and performing than it does. The Lexus is a great around-town luxo car.
And before you all start with the "yanks don't know squat" comments - I have always been a strong VW/Audi fan - and not just because my grand-father wa the chairman of VW/Audi South Africa either...