API: json, xml, csv - which one and why?

[brother7]

A question for developers using the Prosper API.

According to the https://api.prosper.com/" class="bbc_link" target="_blank">Prosper API documentation:
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[Fred]

For tabular data, I like CSV best because it is the least verbose -- field names are specified only once, rather than on every record.

However, CSV does not really support structured data (records containing other records).  For this, I prefer json to xml.