Generally there is misunderstanding of these markups. JSON came along because the JavaScript people found it convenient and more network-efficient (the irony being it's not really). But a million years later followed the schema-validation logic to back-fill deficiencies.

In my opinion, one should go for XML when writing a portable document format of any variety to allow a vast array of schema validators, linters, and so-forth. This makes writing plugins which target a given schema much more portable and easier to write.

It's kind of ridiculous how many times web folks reinvent the wheel. Seriously, get rid of YAML, TOML, JSON. We already had INI, XML/XPATH/XSD.

There's nothing wrong with XML, people are just lazy and so is JSON. It's the lazy, sloppy cousin of XML which was a well-thought-out standard to fill a deficiency in HTML for data.

Honestly though, we should be using something like this: http://openddl.org/