Bitcoin block generation rate has slowed down from 10 mins to almost 15 mins
blockchain.info
blockchain.info
There is more information about the relative hash rates for both chains at http://fork.lol.
Secondly, as transaction fees are a supply and demand system, demand for transactions on BTC (tx demand on BCH is negligible) can shift that profitability ratio simply by paying higher fees. AFAIK miners aren't setup to switch back and forth on a block-by-block basis yet, but I wouldn't be surprised if they start to do that in the future.