The vocal harmonizer on PA3x and PA900 are much easier to use than the one on the PA800, and to my ears is much improved. Actually the PA900 is more user-friendly than the PA3X, but lacks a few of the bells and whistles maybe.
Ketron is also vastly improved. The Midjay had only a vocoder. Audya is way better than the old X1. Roland is a non-player for now, so is not relevant. If the BK9 had a decent vocal harmonizer I probably would have kept it.