This entire thread is pointed in the wrong direction, what you guys are juxtaposing would be like comparing a 350z to a Nissan Pathfinder JUST because they share the same engine.
The G35 is not a luxury version of the 350z, and the 350z is not a sporty version of the G35, they are two different models altogether.
The 350z comes from the Fairlady Z line of cars from Nissan, as I'm sure all or most car enthusiasts will know.
The G35 is a re-badged version of the Nissan Skyline V35.
The Z and G35 are totally different cars with similar suspension, engine type, and engine layout (Front Midship engine layout popular with new Nissan performance vehicles)
Look up a 2003 Nissan Skyline and you will see my point, The G35 and Skyline V35 are built in the same city, use all the same components, even the same paint job lol. Having this argument is like saying a Nissan Skyline GT-R is a "luxury" version of a 1994 Nissan 300ZX, the two cars are completely different.