Well, I dunno, I follow FF7 closely, and lots of BOTH arguments seem valid to me.
As far as I know, none of the ORIGINAL writers of FF7 have given a definitive statement of the story.
Personally, it makes more sense to me that Jenova would be in some sort of control, perhaps using Sephiroth as a puppet. One main factor being the fact that Jenova is an ancient, mystical, otherworldly being, having lived for many years, wiping out entire cultures (Cetra) in the process. The idea that this powerful being would succumb so easily to a human with a few cells injected in during the pregnancy seems laughable to me.
Gotta go back to uni, might return l8r and expand on my reasonings.
