ZCash is corporate and premined. I don't want money to be controlled by a corporation. 'nuff said.
Sadly it will enjoy popularity as the PR offensive is underway already and greed has apparently become the main motivator in the crypto world.
I'm not commenting on the other 2, there is plenty of material for research in this forum.
Edit:
https://news.bitcoin.com/meet-top-3-coins-cryptocurrency-anonymity-race/q.e.d.
When I saw that ZCash was backed by a corporation/organization, I had my suspicions since truly decentralized cryptos like Bitcoin didn't had such thing. That was my only concern, but I guess this would not make it as decentralized as they would claim it to be. Other than that, it could be a great opportunity to make huge profit, if you come in earlier and invest into it.