Much as I hate to be partisan, in this case it is my duty to be so for Plan Z: The Phoenix Project.
So far as I know, only Golden Girl has moved over to work on her project. She is actively recruiting. If people like the direction she takes with Heroes and Villains, then they are of course free to work with her. Everything any of you have contributed and worked on is still part of Plan Z: The Phoenix Project. I would therefore hope that it has, for the majority or even all of you save Golden Girl, been something on which you wish to continue to work, and that you will thus stay here with us.
I would actively discourage people from turning to TonyV to ask which is "official," because he truly doesn't want to be in that position. To my understanding, he will be working with both projects. I hope this does not overburden him, but it is his time and his choice what to do with it, and we're grateful for all he has done and will do for us. He has, amongst other things, his own project that works in tandem with just about any MMO or community-based game, so he may well be able to work with both by working primarily on that.
Make up your own minds, but Plan Z: The Phoenix Project is the project that you've all come to watch form. Heroes and Villains is a new direction and approach breaking away to try things in Golden Girl's style, feel and design. If you really like what she's doing, therefore, it probably is where you should go. If you like what you've been seeing, however, and were planning to continue contributing to the Plan Z you had been following, this Plan Z: The Phoenix Project is your best home. At least, that's my opinion. I am, obviously, somewhat biased. ^_~