Which coin has the strongest features? I've heard each one has it's strong and weak points. I am unsure which has the least amount of weak points combined with the largest amount of benefits.
I'm only going to comment on the technological side. The speculation side is maybe totally different. After all, for the speculation side, there doesn't even need to be a block chain or any code running: exchange IOU are sufficient, if hyped enough. So the market cap, speculation, "making profit" side of crypto, which is ridiculous to me, is not my piece of cake. Speculation has nothing to do with the technology of the coin apart from a sterile "hyping" feature.
I'm interested in crypto for "crypto anarchist" reasons, which I think are the only valid reasons to prefer crypto over fiat. There's strictly no reason to go through the hassle of crypto of one wants to "go to the masses" and "comply to the law". Fiat does that better, cheaper and more reliably than any crypto ever will.
As such, when comparing bitcoin, DASH, ZCASH and monero, my preference goes out to monero, but not because I'm a monero shill, but because the three others have significant no-gos. Bitcoin is great, but not fungible, leaking incredible amounts of privacy information (way, way, way more than fiat does). Bitcoin used to be grass roots, but has become a chinese consortium, and the only thing it has running for it is the fact that it was the first, and hence no suspicion on any premine scam can rest upon it.
DASH was a serious improvement over bitcoin on the privacy side, but essentially lacked the right technology. Bitcoin technology is traceble, and the only thing that DASH did, although very important, was to automate the mixer process. However, DASH had a scammy start. The other problem with DASH is that in order to do privacy "automatically" with technology that is not adapted, it needs a whole messy structure of masternodes, and this invites the other problem of illegal security stuff.
Monero was the clean follow-up on the scammy, but brilliant bytecoin. The new technology proposed by bytecoin, namely ring signatures, solved a fundamental problem of privacy in bitcoin like chains. However, bytecoin started out with such a terrible scam, that a new coin was due, to rescue the technology. However, monero's technology isn't perfect, it still leaks some entropy about privacy, and it is still missing scriptability. That said, to me, it solves an essential shortcoming of transparent block chains, and monero is inherently fungible, and quite privacy oriented. Moreover, it is also pretty grass roots.
ZCASH is a big disappointment. It includes the best privacy technology as of today, better in principle than the ring signature scheme of monero, because NO entropy is leaked with zero knowledge proofs. But it has been set up in a way that is both scammy (the dev tax) and a no-go: optional anonymity. Moreover, it has had a very questionable to be trusted setup. In other words, ZCASH has brilliant technology, but fucked up in its setup.
This is why, as of today, I only see Monero as a serious private coin in the list of the OP. It is really a pity that zcash fucked up so hard. It has potentially better technology. bitcoin and DASH are "old generation" technology to me, with too many problems