With fast changing difficulty, miners will never move all hash to BCH, because it will never be profitable enough, unless BCH price would increase to BTCs level..
We all saw what a mess EDA was. Fast DAA ensures that hashrate is divided proportionally to the price of the coins.
True, but it does not incentivize miners to switch to BCH long terms, as soon after they switch, difficulty rises instantly, so they are best to switch back to BTC again.