Of all the companies you mentioned none of the better ones like Ferrari or Porsche or Lamborghini makes a V6.
Are you so sure that Ferrari haven't used a V6 engine? I think I recall one of Ferrari's most famous cars used that very configuration.
But you are correct that such an engine isn't balanced in the same manner as a V8 will be, but the same is true about a V10 yet it's been used not only by BMW but have a decent career in F1 as well. Imbalance is easily overcome so that is no need to try and use it as a reason to dismiss such a design because the benefits else where out weigh the small disadvantages.
The bottom-line is Vee is better from a packaging point of view and from the view of force feeding it with turbos.
P.S.
Why do you always turn any discussion to an Audi vs BMW debate? I don't.
And why mention the 2.5TFSI? It's been acclaimed by the motoring press and engineers alike as an exceptional engine.