Ugh... Tough call... I just put down a deposit for a 6sp Touring 350Z, which is going to run me about 35K + tax (DVD navigation and other small extras bump up the price). The G35 looks awesome, definitely more refined, but it is a little longer, heavier, and tuned more for comfort than for pure performance. Also, the Touring package on the 350Z has pretty much all the same little luxuries (leather, Bose audio, heated seats, etc.) as the G35. Too close to call, like others have said.
It all comes down lifestyle in the end, I guess. I'm 28, unmarried, and at this point the Z looks like the better choice (especially w/ La Mans Sunset exterior!
), but if I were ten years older with a wife and kids I would probably opt for the G35. As it stands now, one of my friends is getting a G35, so I'll have ample opportunity to compare the two--I look forward to running circles around him!