I went with the Z1 CSC Elimination Kit because I don't want to ever have to drop the transmission again to mess with clutch hydraulic problems
I also recently worked on a later model 350Z that had the revised external slave cylinder since the internal one was failing so much on the earlier 350Z. This is the basis that Z1 used for their design for the 370Z kit. Why did Nissan chose to go back to the internal CSC for the 370Z? The almighty dollar, most likely