While I personally would always use Postgres as first my first choice, I've used both Oracle and SQL Server in various projects in the past. Oracle because we

While I personally would always use Postgres as first my first choice, I've used both Oracle and SQL Server in various projects in the past. Oracle because we needed to run an application that only supported Oracle, and SQL Server because the company I was working at at the time already had a large SQL Server install. Honestly both are perfectly fine databases and I saw no technical reason to replace either if you already have them. That being said, I didn't have to deal with the licensing or the costs, which are the main arguments against both. Everybody I know who has migrated from Oracle to Postgres has done so, not for technical reasons, but to get away from having to deal with Oracles licensing bullshit.