Personally it's the history for me. MySQL started with MyISAM, not innodb.
So if you wanted an actual transactional database back in the day, MySQL was definitely not it. You needed Postgres.
InnoDB was not MySQL. It was an add on. So if I had to use MySQL it was with innodb of course but why not just use Postgres. And after the Oracle acquisition... Yes I know MariaDB. But I'm already on Postgres so...
I'm also curious about this, especially if anyone has operated postgres at any kind of scale. At low scale, all databases are fine (assuming you understand what the particular database you're using does and doesn't guarantee).
Postgres has some really great features from a developer point of view, but my impression is that it is much tougher from an operations perspective. Not that other databases don't have ops requirements, but mysql doesn't seem to suffer from a lot of the tricky issues, corner cases and footguns that postgres has (eg. Issues mentioned in a sibling thread around necessary maintenance having no suitable window to run at any point in the day). Again I note this is about ops, not development. Mysql has well known dev footguns. Personally I find Dev footguns easier to countenance because they likely present less business risk than operational ones.
I would like to know if I am mistaken in this impression.
If you've seriously considered both and then selected PostgreSQL please comment and tell me what drove that decision.
Note: I'm only talking about OLTP. I do see that PostgreSQL adds a lot for OLAP.