58678d68_chmarking_AJAX___JSON_vs_XML____JSON
[Characteristic] Namespaces [XML] Supports namespaces, which eliminates the risk of name collisions when combining documents. Namespaces also allow existing XML-based standards to be safely extended. [JSON] 
No concept of namespaces. Naming collisions are usually avoided by nesting objects or using a prefix in an object member name (the former is preferred in practice).
Benchmarking AJAX ( JSON vs XML )
JSON