[colanderman]

Why not read its extensive documentation (http://www.postgresql.org/docs/9.5/static/), evaluate its capabilities vs. those of MongoDB with respect to your particular use case and decide for yourself?

SQL has never ever been meant for "editing documents", doing so is certainly not considered "basic functionality" for anyone whose use case is best served by a RDBMS, and you'll likely be displeased by the performance of such in Postgres (or any other RDBMS) if that is something you consider "basic functionality".

(FWIW: what I've found to be the typical use case of JSON-in-SQL (or XML-in-SQL) is that of storing opaque JSON or XML blobs generated by some external service, which could perhaps benefit from indexed lookups within this data. If you're designing your main SQL database around JSON you're probably doing something wrong.)