The closest competitor to Monero is Zcash, which was launched in October 2016. As opposed to Monero, 10% of all the supply will be distributed to the stakeholders in the Zcash Company - founders, investors, employees, and advisors (see story above). Zcash uses an advanced zero-knowledge proof cryptography called zk-SNARKs. All the transaction data is fully private including metadata, which is encrypted. Zero-knowledge proof means that the validity of data can be proved without revealing the actual data because it is secret. Therefore, there is a real concern that the total supply cannot be verified because the system is too private. If the trusted parties that are controlling Zcash were to collude and secretly create more coins, it would be impossible to tell.
Another difference from Monero is that the transactions are transparent by default and optionally private. Currently, most of the transactions on Zcash are not private, which makes it easier to identify the private ones through traffic analysis. The private transactions are quite resource intensive for users as sending a private transaction takes about 3GB of RAM and an average of 40 seconds to perform the encryption, which is one of the major reasons that it's rarely used in practice. Zcash's next major upgrade, codenamed Sapling, should significantly decrease both the resource requirements and the time needed to send a private transaction. Zooko Wilcox, CEO of the Zcash Company, stated that the intent is to upgrade to all private all the time eventually. Even though the technology of Zcash is more advanced than Monero, it has yet stand out and there are still some unresolved issues.