Keyed curves vs. Bone driven contoller: which is better for performance?

For driving corrective morph targets, which one is better?

For example, you have corrective morphs for arms and legs. You can drive them from curves or from the anim bp. Suppose you have many of them, something like few dozens of them, like in boy and kite example.

Which way is faster and which one takes less memory?
Also, how many morphs applied in the same time is too many?