Really
JSON is better (and XML is crap) it's ridiculous, it's obvious, it's clear cut, and when people "don't get it" you start resorting to irony
Like this:
> Enclose the /element/ in matching delimiters, not the tag
Let's compare them
<blah>foo</blah>
To json
blah: foo
1 - size (json wins)
2 - matching. Here's an exercise, try splitting json with sed, and then try with XML. Sed is a good exercise, because it's limited to simple grammars, so it kind of gives an idea how much trouble it is to parse each one
3 - redundancy: what would mean if the line was <blah>foo</lala> This is a mistake, right? But I can assume the tag name is blah and the data is foo. This is a glaring redundancy in grammar, bound to cause trouble.
Not to mention working with json data (like python) is natural compared to work with XML data.