ZYX carbon fibre stylus vs boron

A few years ago I had a Zyx mid level cartridge with an aluminium cantilever. I liked the cartridge so decided to upgrade to one of the newer CF cantilever cartridges, that was much higher in the range. But I could never get it it to sound quite as good as the earlier cartridge, despite 30-40 hours of running in and trying many adjustments. It just sounded a bit dry and colourless by comparison, so I sold it on.

A bit later I bought a new but older model Zyx cartridge from 2Juki, one of the higher end cartridges with a boron cantilever. This sounded fantastic, much better  than the CF cartridge I tried briefly. There was a return of saturated tonal colours, as well as the speed and dynamics I was expecting. I liked this so much I picked up a second one as a spare.

It is possible that my issue with the CF cantilever was a one-off issue with that specific unit, or may just have been insufficient break in. But I was sufficiently unimpressed with it to avoid trying a CF cantilever again. 

rossb, I think you hit the nail on the head.  That is pretty much how I "hear" carbon fiber parts anywhere near the signal path.  I've got an original UNIverse, with boron cantilever.  It's excellent.

I have a ZYX Ultimate 4D-X which has a carbon fiber cantilever. My previous 4D had a boron cantilever. I can only go from memory, but it seems there are only subtle differences between the carbon fiber and boron cantilevers. I do not perceive any faults with the carbon fiber version. I listen to a lot of rock, jazz, and classical. The 4D is darn near perfect in my system. I also have a retipped Denon DL-S1 with a boron cantilever and microridge stylus, which I also like. The Denon perhaps has a tad bit better detail, but the ZYX exceeds it in soundstage and image size. The ZYX is my favorite as it seems to better capture the scale of the music. I rank the ZYX and Denon above my Dynavector XV-1S. Others I am sure would hear it differently.

Carbon Fibre Cantilever differs from other typical cantilevers produced throughout the years of R&D with certain materials then being selected the Cantilever Role.

CF is not a Natural Occurring Material, it is a multiple of an Carbon Element.

Many Cantilever Materials are Elements with their own Element reference on a Periodic Table.

In a nut shell a Purist of pure material, sometimes to be found as a Cantilever with a coating of some kind.     

 There are natural material Cantilevers not from an Element.

Carbon Bonded as a crystalline material to produce a Tow, is then put through a process of becoming a Composite to become a Fibre.

A CF Cantilever is to be produced from multiple thousands of Carbon Crystals and a Resinous Material to produce the form of the Cantilever. 

As a Cantilever it seems very very unique as the Structure, how that transfers energy and a particular amplitude would be interesting to learn.  

Well the cantilever is not supposed to transfer energy per se; it's supposed to transfer the motion at the stylus tip into motion at the coil or magnet or iron end of the cantilever, with minimal energy losses along the way (like in the form of resonances).  In theory, that might be an advantage of CF over pure metals, if CF is at least equally as stiff as a given choice of metal. But like you suggest, it depends upon how the CF was made; not all CF is created equal.