Well, since we don't talk much about MBTI here anymore anyway, what's keeping you here, Ath?
I assume the general discourse and/or the people you care about or like.
As far as "more valid" theories, I wish Gatsby was here, he was very knowledgeable in the theories that had more actual statistical validation. I know the Big Five traits have been tested and verified much more... so that provides a partial cross-link to related MBTI traits. But MBTI is much more of an experiential/theoretical framework, built on an intuitive basis, and thus is not necessarily correct.