[jcrawfordor]

One consideration that's worth thinking about is that XML serialization is larger (often not insignificantly) than the same data serialized as JSON.

On the other hand, XML can make error handling much easier by schema-validating received documents and thus rejecting a large class of invalid inputs at an early stage. This is particularly helpful if you're making something interoperable, like a public API.

So even when you're just using a library, there are ramifications to the decision.

[cm2187]

Correct. But in the order of things I care the most about, using angle or curly brackets matters a lot less than problems like: can I serialize multi-dimensional arrays, dictionaries, arrays of bytes, etc.