Hi,
Very good.
the main reason as far as performance where I think everyframe as an edge is that actions do not need to re start every update.
if you have an action that instantiate several objects, get some components on the targeted gameobject and all this, using an everyframe based action always there means only ONE instanciatation for the whole cycle, possible the whole game. If you do a next frame event, states are entered and left every update and therefore each and every action instantiates, initiated destroyed, garbage collected somehow by the memory managed and all its internal stuff as well.
So, yes for small cases I am sure nothing will be noticeable, but for larger project, that would certainly become a possible issue. This also very much depends on the actions used in that cycle of course.
bye,
Jean