It would most likely be the I or P. I really like the extroverted intuition aspect of myself and the Extroversion wold seem like a less radical change. Just a slight twist in perspective. It would seem more normal, like less of a transition. I'm very content and comfortable with my type so I wouldn't like any radical alterations.
I probably get along with INTJs and ENTPs the best anyways, we each offer something different and valuable and all perspectives are welcomed usually. Even if we sometimes don't agree. So if I were to choose types it would alternate between that tri-fecta.
1. I -> E
2. P -> J
My cold, snide, intellectual life is just a veneer, behind which lies the plywood of loneliness.