General question on Carbon fiber tonearms versus aluminum

Another thought is aluminum may sound better with MM cartridges and CF with MC cartridges.

@slaw Why would one material sound better with MC cartridges than MM?  

@testpilot Agreed, although  I was thinking more in general terms.  That is, it could be easier to make a better sounding tonearm with CF than AL.  Clearly, it is that way with bicycle frames, it is far, far easier to make a frame stiff in one direction and flexible in another with CF, or make it a more comfortable ride with less vibration than say AL or even steel.   

I'm not sure that either aluminum or carbon fiber is inherently better than the other, but magnesium is certainly one of the best materials for a pickup arm - such as is used by SME and Technics on some of their arms.

Clearly, it is that way with bicycle frames, it is far, far easier to make a frame stiff in one direction and flexible in another with CF, or make it a more comfortable ride with less vibration than say AL or even steel.  

Not exactly apples to apples...

You might want to look at this video:
https://www.youtube.com/watch?v=Lb4ktAbmr_4

Since this is only a matter of opinion, I would offer my opinion that I have not found most carbon fiber pieces to be good for verisimilitude in my audio systems. In particular, that has been true of the very few carbon fiber tonearms I have heard. They have tended to produce a sound that seems overdamped, lacking in dynamics. However, they have tended to cover up certain kinds of flaws in certain LPs, and make them sound “good”. But not great.