Depends on the transform.
The animation itself can be whatever, probably, in the end you have to swap out the blueprint from character to vehicle to provide the correct motion for instance.
Morph vs Bones on a skeleton have similar costs as they essentially do the same thing - shift vertices at run time.
If you are using this animation at the start of the game, then you obviously don’t have to swap anything, you just disable movement while it plays and you are good to go.
The determination on what you use should be done by you with project specifics in mind.
I would say combine both morphs and bones for the best possible effect.