Question Performance Optimization per large numbers instances, Blendshapes in animations VS Bone-based rigs?

I have been trying to get an answer to this,

but, in Unity, what uses more resources (CPU/GPU), facial animations/animations making use of Blendshapes or Bone-based rigging+skinning?

I am trying to save on CPU usage, but I am also just wondering what Unity says themselves about what we should use when trying to cut down on resources, like whats prefered.

I also realize some assets can make use of vertex animations, I was wondering about that as well.