Actually, we had the same setup: GC Coil + Shocks. Same springs setting and I can tell that mine handles very different. Both have the same year and model, uses the same size of wheels and tires.

I then switched to Tokico RAk501 Competition Full Coilover setting and also notice a huge difference as well. This is on my Accord.

Now, about the G35, I've heard many people using D-Specs + Eibach and have good result. I don't know how that compares to the 350Z since the G is heavier and different in handling. People also recommend Tein Flex, but it'd very stiff.

Some uses these NEW Generation Coilover Like Ksports, Megan, or FF with custom spring rates and have good review. Then again, the majority of the people are bashing these new comers because of 1 reason: They're new and haven't established themselves really well. Also because they made in Taiwan. Well, guess what, others made the same way as well (HKS, Apex, etc.) Tein is different because the use the different scale. But that doesn't make them better.

Stock - stock replacement application, Tein or HKS are better because of the difference in spring rates. These "NEW" coilovers come with VERY STIFF Spring rates for the Z and G. But most of the distributors allow you to choose spring rate, and some actually allows you to revalve and caibrate the shocks to the new rates, thus allow you to optimize your handling.

Couple guys I talked to had these on their Gs, and also on their Hondas and love them very much, they even says that they're better than Koni Yellows + Custom GC Rates, which is considered to be VERY Good.

Anyhow, just my feedbacks on hearsays. I absolutely don't have any experience with these on the G. I'd like to try out one day though. Hope this help you make your decision.