I feel like I am missing some mentions here like DeepOnion and CloakCoin which should be added to the list. All the coins mentioned (excpt Bulwark) are large to mid-caps and if you think Privacy sector will have a boom in 2018 I would look at the small cap coins. I think it will be a lot like how the ALTs surged in 2017 compared to BitCoin that the privacy small-caps will surge in comparison to Monero and ZCash. Take time and do your research into the small caps, such as Bulwark, DeepOnion, Cloakcoin and similar.

I have done my research and if I should choose one small-cap coin to go for it would be DeepOnion. The coin has a already launched a nice unique feature in DeepVault (unique among privacy coins), which is basically file verification on the blockchain. Next step is to release DeepProtocol (Stealth Addresses), which makes it possible to de-link your identity from the coins you receive, no single address will hold your coins and it will be ipossible for an outside observer to say which addresses belong to you. These are just the early steps in the project and that is when you need to get in, if you are looking for the bigger gains. You can find out more about Stealth Addresses in articles such as: Stealth Address upcoming and other DeepOnion features in the DeepOnion Forum and Webpage.

But as DataDash (Youtuber) says, don't put all your eggs in one basket, diversify a bit, find 2-3 privacy coins that you think have the tech to make it big. If the privacy sector booms then it is the small-caps that will have the biggest gains and if one of your choices is the correct one expect some nice returns.
I am not a financial advisor so this is just my views on the matter.