Missing links to benchmarks.
Also, Json is not really a good baseline for comparison. If you support binary data natively in the format, you should compare it to Bson.
Bson is just terrible. Just as a taste, arrays are encoded as key-value, where key is the array index converted to a decimal string and then stored as zero terminated string with 4 byte length prefixed to it. It boggles the mind why somebody would design a format like this.