JSON and YAML implementations are just as simple as their formats, you can choose from very many of them.
Question: How do JSON parsers compare to XML parsers from performance perspective?
I wrote sample inputs in XML and JSON. The same data, basically. For XML, I have made two input files. The first is the 'traditional' XML, no attributes at all. The second uses some attributes. The third is the JSON version. I used very few XML apis, only the ones packaged into JDK, this is a bit unfair because the alternative XML apis may be a little faster than the default. I have made a test a few years age and that showed them not so much different, so I was more interested in JSON. With JSON format, I used 5 different parsers: json.org, jackson, jsonlib, jsonj and gson.
Even the slowest JSON parser is faster than the XML parsers of JDK, also the format is more compact, looks like it is win. Jackson is much faster than the rest. It's website is right, it is very fast.
Test source code: here.