If you're using a strongly typed language, XML even has one (IMO) massive advantage over JSON: You can use XSD to define a schema declaratively. This means you get
(1) lots of general tooling support, in particular you get at least decent editor support for your config file, and
(2) you can autogenerate the code needed to read your configuration into structured data without having to do any unnecessary duplication of "key names" (tags) as you have to with e.g. INI or JSON. You also get the data sturctures themselves for "free" (based on the XSD).
Alright, it's not the end of the world to not have these things, but they're both very nice to have.