You'd have to be an idiot to use Zerocash, considering who funded the research.
This^^, Zerocash has too many flaws. Rather use Darkcoin.
Zerocoin and Darkcoin have flaws.
Monero on the other hand...
Darkcoin will be implementing Ring Signatures and I2P, plus it's existing masternodes which is better anonymity than Monero/Bytecoin I'm sorry to say, we also don't know that much about the CryptoNite protocol.
Masternodes can be traced and DDoS'd, Monero's technology is safer. By the time Darkcoin adds Ring Signatures, Monero will take the lead as the to-go anon route of the crypto world.
Darkcoin isn't just implementing Ring Signatures, but I2P as well...those two combined with Masternodes gives a much superior anonymity than just Ring Signatures alone like in Monero....