You folks are too bias. The Z06 was faster.
The Z06 did 0-100 in 8.5 seconds and the GTR did it in 8.9.
The GTR did better 0-100-0, but they had a better reaction time in the GTR (time between WOT and hitting brake pedal).
GT-R: 0-100 = 8.9, 100-0 = 4.3, accel to brake reaction time = 0.6
Z06: 0-100 = 8.5, 100-0 = 4.5, accel to brake reaction time = 1.0
Thus, if you subtract the difference in reaction times, the Z06 was not only faster 0-100, but it's faster 0-100-0 also!
The Z06's lead would've been even larger had they kept going (the article mentioned that the Z06 was accelerating harder past 100mph....this also hurt its braking time).
The Z06 is even more impressive because it has inferior tires and hit the market a full THREE years before the GTR.