I cross shopped with the S4 and found the DCT fantastically quick, but the shift maps seemed "off". If you opened it up but then let off the transmission would get all confused and start jerking you around. OTOH the 8 speed sport auto was incredibly smooth in sport mode really no matter what you are doing.
edit: of course this is more directed at the VAG 7sp shiftronic rather than DCT...
Not sure if this matters, but I've read servicing DCT can be a nightmare if something goes wrong, not to say that the 8 speed would be any different.