Been awhile since I looked at the 350Z so some of my comments may be out of date.

The Z is much slower than the SRT-6 in any accleration test but does handle better.

The SRT-6 engine has much more potential for additional power. Last time I saw a test of Z's with aftermarket parts including cams, superchargers, turbos, etc. the modified Z's were not if any faster than stock.

The G35 (not sure about the Z) has problems with eating its front pads and rotors.