I saw some head-to-head review too in a dutch magazine. Their conclusion was that the TT was as fast as the 350Z, and much easier to drive on the limit, but less of a "true" sportscar due to the lack of feedback and that it was so "safe" to drive. On their test track they had about the same lap times, but it took them more laps to get there with the 350Z, compared to the TT. Its basically a true Audi in that aspect. Fast, comfortable, safe to drive on the limit ---> boring after a while.
Thats what they said at least
Conclusion: you want "the best" car, get the TT, you want the car to give you the most thrills and fun, get the 350Z. I think i ll have to agree on this. Depends on what you expect from a car. I dont think trying to drift a FWD car with a haldex to get RW power (max 50%) will be the same than drifting a RWD car with an LSD
Now i must say on the looks department, the Z looks way more like a sportcar than the TT dough