Comparing the 0-60 time is only part of the story. The difference in power between these 2 cars will become more apparent the faster they go. Look at 1/4 times etc. As for handling, not to knock the G35, but smaller/lighter is always better, so don't expect the G35C to handle like the RSX-S. It wont, but it will be very sporty. Also, the 350Z will handle marginally better than the G35C because of it's slightly smaller wheelbase and lesser weight, but it's only 2 seats.
If I were you, I'd go for the G35C 6MT. It's a great car and it's got a good aftermarket. Once you go move from VTEC car to a car that produces copius amouts of torque below 3000 RPM, you wont go back:)
CD