One important difference is that you don't need to extract the values to create an index. E.g. in Mongo I believe you still have to decide which keys to index.

One important difference is that you don't need to extract the values to create an index. E.g. in Mongo I believe you still have to decide which keys to index. A GIN index on top of jsonb in PostgreSQL will make it possible to do an indexed search on any key, not just those that are specified at create index time.