7 Answers
New Answerdepends like many options xml nice <list name="todo"> .... but json nicer to read and write and less data no <><><> and is preferred in many apis (less data - speed, bandwidth) it depends on use
For me the choice depends a lot on the language with which you want to make requests to the API. There are languages that have greater support for JSON or XML, and within the ecosystem of those languages, the use of a particular option is also widely recommended (either because of its support or because it adapts to the philosophy of the language). Personally I like to use more JSON. I consider it simpler for me.