PostgreSQL is an object-relational database, while MySQL and MariaDB are purely relational databases.
Advantages of PostgreSQL:
- Object oriented relational database (ORDBMS)
- Supports more data types (arrays, json, maps etc.)
- Offers more features (like Table partitioning, Point in time recovery etc.)
- Is more suitable for using of complex queries and frequent write operations
- Multi-version concurrency control
PostgreSQL can be faster mainly when making a complex operations. If you do mostly simple operations, you can get better performance with MySQL or MariaDB. These databases are more suitable for standard websites.