Just adding my $.02
Looking really quick, it looks like the Infiniti is another 200lbs heavier, a little less powerful (7hp less), comes stock with a navigation system... that's what I can see at a glance:
Inifiniti vs.
Nissan
I am sure the Inifiniti has alot of other bells and whistles that come standard that the 350z doesn't. But the main thing: I hate the Nissan's door handles while I love the Infiniti's tail lights...
Again, just my $.02
-Ducky