I know it's an old thread. But very interesting... I am from an 06 G35 coupe to an 09 370z. I actually still have the G. I consider the G as a performence luxury coupe and Z as a true sports car. It really depends on what you want. In my case, I want a true sports car. So I went to Z eventually.
As both G and Z driver, I can tell you this - people does give me thumb ups time by time while I am in the G. But when I am in the Z, people give me thumb ups ALL THE TIME even following me taking pix. Btw, my g35 was pimped out while my z is born stock. So consider this as a factor too!:P Like me, now the first mod I want to do is to tint my windows to get some private.