It's simply that you can add one of those (or both...) into your RPG to get some new stuff in it.
Prescience/Premonition :
Has a sound that plays and explosions to hide what's being changed into the actual screen view. During the explosion, you could, for example, add some monsters and like that, the hero could know there is a rush of ennemis that will be there soon so he can decide to hide or to fight...
Flashback :
Explosions too (to recycle the terrain like that, you won't lose a bunch of terrain only for a simply cinematic) and normally add a part of storyline and NPCs...
Well, that's it
None.