Question for Aras || Farfarer regarding hypothetical performance difference between implementations

I hope this is appropriate, and I think it will benefit many others to know.

(Unity DirectX 9)
In a situation where I have a NxN mesh plane, and I wish to move the vertices every frame.
Which of these two implementation is faster, how much faster is it, and why:
.

1. Passing the vertices and normals to a Mesh instance. (Ignore the time needed to calculate the normals, I can handle that very efficiently outside Mono)
2. Passing a height map to the shader as texture, and...

Question for Aras || Farfarer regarding hypothetical performance difference between implementations