Too Long; Didn't Read
BEAM on Confidentiality, Scalability, and Auditability compares Monero vs. Zcash vs. Bitcoin. Monero scores very well on confidentiality, poorly on scalability and poorly on auditability. Zcash uses zk-SNARKs — a novel and very advanced form of zero-knowledge cryptography. ZCash has excellent privacy features, but there is no complete proof of completeness of the transactions. The size of an average transaction is about 2kB which is still many times greater than in Bitcoin.