Why do you discuss the question: "Bitcoin
or Zcash?" I think the answer could be: Bitcoin
and Zcash! Both of them can exist side by side. The use of Zcash´s anonymous transactions will increase and has become easier since the "Zcash wallet and full node for Windows" (
https://zcash4win.com/ ) was released. Zcash will be one of the most important coins in the next few years. Just like Bitcoin, Ethereum and Monero.
I'm becoming more impressed with Dash all the time. The ASIC miner makes it harder to mine but they have a winning marketing strategy. Zcash seems to have dropped off the radar and the coin is suffering because of it. Dash are actively working to build their currency. Monero was impressive last year, but seems to be stalling at the moment.