[acabal]

While both are good fits for their specific use cases, I think JSON won as an medium of exchange because unlike XML, JSON is dead simple to parse and ingest programmatically.

What makes XML so unergonomic to ingest is 1) attributes, which don't map cleanly to a basic data structure that you might find in a programming language, and 2) namespaces, which are extremely, extremely tedious to program against.

Programmers are going to use the format that's the easiest to ingest and manipulate. JSON wins in that regard, hands down. Every time I need to write logic to ingest a namespaced XML document I heave a deep sigh and brace myself for another long week of fighting with LXML. But with JSON it's as easy as `json_decode($str)` and move on with your life.