If you widen JSON to be strictly pure JavaScript object and value literals (e.g. allow comments, non-string keys, use of constructor calls, etc) then JSON is more expressive because each child of a JSON object itself is a JSON object - whereas an XML element has two distinct types of children: child-elements and child-attributes, and the expressiveness of attributes is considerably limited compared to child-elements. Granted, JSON provides no inherent way to denote an attribute compared to a child element, but remember that XML restricts you to a single complex child element collection, whereas with JSON you can have multiple properties containing children (unless you want to argue that named element children could correspond with named complex properties in JSON - then it's just a matter of syntax).