G35 hands down in my opinion. It has 2 more seats (though very small), is classier, better looking in my opinion, and according to car and driver has better stability in the corners.

G35's always make my head turn. 350Z's only make my head turn when they are modified.

Also the Z doesn't have a moonroof which is a must have for me (or atleast they didn't have one the past few years, not sure if they added it as an option)