In the absence of interoperability concerns, i don't think there's much in it. There are good libraries for all of them in all languages; some of them are built-in, some aren't. Yur interface to those libraries will be narrow - just in data-access code - so if one has a painful API, even that doesn't matter much.
JSON is, for me, the most pleasant to edit by hand, which is a small plus.
YAML can handle non-tree data structures using the &/* notation. Neither XML nor JSON have a built-in way to do that. Your use doesn't need it, though.
