Well the G35 should be double the price of an 11 y.o. gsx. Since the gsx is modified it probably gets pretty poor gas mileage (not that the G is great on that). Also consider the fact that the gsx will have far more maintenance issues since it is modified and much older. Consider the resale value of the car too, how long do you plan on owning it? Not to mention that the G is much more stylish.
If you were considering these two cars the G is a no brainer.