For the past ten years, developers have made a game of comparing MySQL and PostgreSQL, with the latter seen by many as technically superior.
Those who support PostgreSQL argue that its standards support and ACID compliance outweighs MySQL’s speed. MySQL remains popular thanks to its inclusion in every Linux Web hosting packages, meaning that many Web developers have used it; but ever since Oracle bought Sun, which owned the MySQL copyright and trademark, there have been widespread concerns that the platform isn’t quite as open-source as before. Meanwhile, PostgreSQL not only got faster, it also added JSON, making it one of the few relational databases to also support NoSQL.
I’ve worked with both databases for over ten years and think MySQL has done a great job of improving itself to keep relevant, but I have to confess to favoring PostgreSQL. There’s less hassle with licensing, custom data types, table inheritance, a rules systems, and database events.