I can't quite say just at the moment. I'll have to play around with all the specs during the pre-patch and see what I enjoy most. Typically I really enjoy Affliction for leveling due to the mobility and self-sustain, whereas Destruction is at the bottom of my list since it's been lacking in mobility and survivability since Pandaria. Demonology has the potential to be the fun shiny new thing, but from what I understand it's lacking in instant cast abilities for mob tagging at the baseline.