Hmm, Raven or Delphia… Fantasy Magic world or post-apocalyptic rebuilding… the other girls are all interesting and have their merits too but these two stand out the most… the chance to rebuild society through advanced Science! or living for centuries with a cute tsundere witch (and maybe building our own little magic kingdom somewhere along the way where we can start working on improving it's perception). As is usually the case I'd probably go Fantasy over Sci-Fi, plus Raven is way cuter :p Bring on the sorcerous powers!
Maybe Raven can even help me find a way to find those other threads, they were once connected to me right? It would be something to look into anyway.