I prefer the Radius CX because the clutch lever feels alive, and I like to slip the clutch when climbing hills manually. However, the CX will require extra attention for long life and those who don't check free-play will be victims of a pre-mature clutch pack failure. The Z-Start Pro is old technology and continues to be a fan favorite for XC riders. The clutch lever feels dead, but you can still override it when needed. Basically, once the Z-Start Pro is installed properly, it's great.