Having answered this a ton over the years, don't want to really take shots at MySQL. But Postgres stands in pretty unique ground.
1. It's solid as a really reach data platform (more than just a relational database). It's extension framework is quite unique compared to others. It's JSONB support was the first among other relational databases and is feature rich and performant. Multiple index types. Transactional DDL. The list goes on.
2. No central owner. A lot of open source is source code is open, but it's maintained by a central company.
3. I mentioned extensions, but really that is understated. It can do really advanced geospatial, full text search, time series, the list goes on.
1. It's solid as a really reach data platform (more than just a relational database). It's extension framework is quite unique compared to others. It's JSONB support was the first among other relational databases and is feature rich and performant. Multiple index types. Transactional DDL. The list goes on.
2. No central owner. A lot of open source is source code is open, but it's maintained by a central company.
3. I mentioned extensions, but really that is understated. It can do really advanced geospatial, full text search, time series, the list goes on.
Having explained this a ton of times first 10 years ago - https://www.craigkerstiens.com/2012/04/30/why-postgres/ and then again 5 years later with and updated version, most recently tried to capture more of this in an updated form on the Crunchy Data blog - https://www.crunchydata.com/why-postgres