All this talk about which car will "beat" the other car is amusing to me. What about the driver in all of this? Most people will never be able to drive these cars at their limits. As such the choice becomes simple. Get whichever car you subjectively enjoy more, everything considered.
2014 Audi S6 * 2015 Audi S3 * 2015 Porsche Cayman GTS
Former 2011 BMW M3 owner