EnterpriseDB has created a framework for benchmarking performance of Postgres and MongoDB. Our tests showed Postgres outperforms MongoDB on key workloads.
We’ve made all the resources available for running benchmarks and are inviting the community to build upon what we started. Further, we’ve made the materials, including a technical deep dive into the NoSQL capabilities in Postgres as well as code examples for implementing JSON/JSONB and HSTORE Postgres, available without registration.
Let us know what you find out if you run a benchmark.