You've got to know when each is suitable. Doing REST properly in JSON involves hacks and trade-offs that you don't have to make with XML. The classic example

You've got to know when each is suitable. Doing REST properly in JSON involves hacks and trade-offs that you don't have to make with XML. The classic example is how you encode a link with a relationship - XML is rich enough to make it trivial. With JSON, you either have to specify a microformat, or rely on mutually agreed regex-matching rules on raw strings (which sucks, but might be enough in a restricted scenario). Then you've got namespaces, entities and validation - all things which might cause someone to say "I'm inevitably going to need X in all my applications, therefore JSON can never be suitable." They'd probably be overgeneralising, but I can certainly see how it would lead to a preference for XML over JSON.