After watching interview after interview of the new houseguests for BB15, I've ranked who I think will be the strongest male and strongest female.
Male: Nick
Right off the bat, it is obvious Nick can be kind of a douche. Although this is true, that may disappear once he enters the house. I feel a sort of alpha male vibe coming from him, and ultimately he has the most potential to be the final male standing.
Female: Kaitlin
Picking a strongest female was the hardest for me to do, but Kaitlin takes it home (with Amanda at a close 2nd). If Kaitlin is as smart as she thinks she is, she will have NO problem taking down everyone else and making it to the end.
Other Comments:
Elissa, being Rachel's sister, will definitely be around for a while considering production's influence in the game. BUT this girl will be evicted sooner or later regardless of how much production wants her around strictly because of who she is.