As of November 2018 however, the v10 preview of AzCopy is vastly improved. Firstly, it runs cross-platform on Windows, Linux and macOS (it is open-source, and appears to be written in Go). Secondly, it has more sensible command-line switches. Thirdly, and most importantly in my mind, it includes the much-awaited sync option. This has been a long time coming.
Click through for a demonstration of this synchronization option.