This is interesting: https://medium.com/@BillionairePal/the-strange-math-of-bitcoin-cash-mining-or-why-not-mining-is-the-optimal-strategy-for-bch-8c5dcedb7fed to mine or not to mine BCH.
That is very old, and not relevant anymore. BCH changed the Difficulty Adjustmend Algorithm in November last year. The new DAA adjusts on each new block, averaging over last 144.
Native phone wallets also a big challenger: "New York City subway will replace MetroCard with Apple Pay tap-to-pay starting in 2018"
https://goo.gl/6CcXtQ
