I would add that it had a better reputation among users of "serious" databases. I first heard of Postgresql at companies built around big, expensive Oracle data

I would add that it had a better reputation among users of "serious" databases. I first heard of Postgresql at companies built around big, expensive Oracle databases, managed by serious, battle-hardened DBAs with long experience with Oracle and DB2 and other big-iron databases. The ones who deigned to have an opinion about open-source databases spoke very differently of MySQL and Postgresql. They were openly derisive of MySQL and laughed it off as something that nobody who knew databases would ever use, but with PostgreSQL, a little bit of respect showed through their snobbery. They couldn't imagine building a business around it (they couldn't imagine building a business around anything that didn't cost the price of a decent car per CPU core) but they were willing to admit that the people who built it had probably seen a real database before, and maybe it was suitable for some non-business-critical uses where Oracle's licensing was cost-prohibitive. That left an impression on me and developers around me such that later, when we were in positions to choose databases for projects, we felt much safer going with Postgresql than with MySQL.