I agree with you. I tihnk Nine was volaitle at time, but Ten was far more unstable. The Nine we saw had Rose, and later Jack, as a stabiiizing influence. His companions were not ripped from him. He left Jack behind and Rose came back for him. Ten was destroyed by what happened with Rose. I thought he was seriously comtemplating suicide in that Daleks in Manhatten two parter. More than once.