I have no idea what your history is, but if you have any type of variety to your symptoms, then I think monotherapy is likely to be inadequate. It would never work for me. I get psychosis all the time, mania regularly, and of course, some depression as well. I need meds that target different symptoms and I have never found a single med that could reliably do all that.
That said, if I had to pick just one--and I am on 25 of Abilify--it would without question be my lithium. It is the most effective bp med overall that I have ever been on, by far. Now, if it prevented psychosis, it would really be a miracle drug...