58678d68_chmarking_AJAX___JSON_vs_XML____JSON
[Characteristic] Learning curve [XML] Generally tends to require use of several technologies in concert: XPath, XML Schema, XSLT, XML Namespaces, the DOM, and so on. [JSON] 
Very simple technology stack that is already familiar to developers with a background in JavaScript or other dynamic programming languages.
Benchmarking AJAX ( JSON vs XML )
JSON