Personally I belive that optional privacy decreases the overall privacy of the cryptocurrency. And I do not believe that you should evaluate a project by the quantity of coins.
Zerocoin privacy is optional, yet it does not decrease overall privacy. In zerocash, on the other hand, it is more like optional transparency longterm, which is beneficial.
I think the market appreciate and understand more ZCash than Monero. The listing on Gemini might be showing this, also other important milestone covered by ZCash.
true, impossible to predict what the market chooses as it may or may not be the one that is technically better (not saying a particular one is, just that isnt a fool-proof method)