On Dec 2015 I have done a similar benchmark on postgres vs mariadb vs mysql, however I had done some serious mistake on the benchmark and caused the result to be biased towards MySQL.
Therefore I had enhanced the benchmark. The benchmark script and how to setup is at this Github Repo.
So recently I want to find benchmark for RDBMS between MySQL/MariaDB and PostgreSQL. To my surprise, most benchmark result is outdated, therefore I have decided to benchmark them, using MariaDB(MySQL) [10.0.22(5.6.26)] vs PostgreSQL [9.2.14]