Hi,
Ultrasonic will dissolve anything that will dissolve in hidden places such as blind galleries etc. as the action continually "explodes" the liquid in minute bubbles, however it will struggle with blockages that will not saturate with the liquid being used.
Vapour blastings main drawback is that it only works where it can be directed and it can force dirt etc deeper into blanked off galleries and compact it.
Vapour blasting is superb for items that have no small drilled galleries where the blasting cannot reach, so blast the outside and other parts, and use a sonic bath for clearing the drilled galleries and dead ends, best of both worlds.