I prefer the latter. After all that's how she is in the Manga. They have ChiChi. Let her be the fighter. Besides everybody knowing how to fight and being powerful wouldn't really be that great. None of them should be able to stand up to Piccolo except Gokou so it be kind of stupid to see Bulma trying to fight Piccolo.
I have faith that Spike will keep at least the Piccolo part of the movie good. And I don't care if we get to see Piccolo until the movie or not I just want to see how it looks all put together in a preview of it. Not that it really matters since this is one of the movies I know for sure I am going to see no matter what. Plus I went to Speed Racer...this movie can't be at much a disappointment to me as that was.