While I use MySQL extensively, I don't really know Postgres so I can't really compare the two. In my current project, I opted to use MySQL because Amazon Aurora didn't support Postgres at the time and I wanted replication performance and serverless autoscaling for a low level read workload that could be randomly very spiky.

Today, both databases are well supported as a service on major cloud platforms. Postgres does have some performance characteristics that lead Uber to drop it [0], but this in itself is not a reason to not choose it, because most teams don't have their kind of workload.

If I were to start a new project today however I would seriously consider Postgres given that Oracle is in my opinion fairly hostile. For example, they re-licensed the .NET driver from LGPL to GPL so that anyone updating would either have to buy a commercial license or open-source their entire product. While there are OSS .NET drivers, this move alone is enough to make me think twice about using it again for a future project.

[0] https://www.uber.com/en-RO/blog/postgres-to-mysql-migration/