The only problem with XML is the verbosity of the markup. Otherwise it's a nice way to structure data without the bizarre idiosyncracies of YAML or JSON.
replyXML has its own set of idiosyncrasies like everything being a string. Or no explicit markup of arrays. The whole confusion around attributes vs values. And many others.
replyJSON has its own set of problems like lack of comments and for some reason no date type.
But in the end they are just data file formats. We have bigger things to worry about.
I mean, XML has its own bizarre idiosyncrasies like the whole attribute vs child element distinction (which maps nicely to text markup but less so for object graphs).
replyI would say that the main benefit of XML is that it has a very mature ecosystem around it that JSON is still very much catching up with.