Why is it that every time a database gets mentioned it turns into PostgreSQL vs MySQL ?

I've worked with both, they both have their learning curve, whatever you already know is going to be 'easier' to you because you don't have to unlearn any habits, I wouldn't advice anybody to use either until I know more of the intended application.

He specifically mentions having experience with Oracle. This will make PostgreSQL easier to learn.

Ok, I see. Oracle's implementation of SQL being closer to MySQL's would be the reason then I assume, I don't have any Oracle experience.

Yes, but the other way around (Oracle's implementation of SQL lines up closer to Postgres). Also, Postgres has a procedural language based off Oracle's PL/SQL language called plpgsql, so if you have experience in one, learning the other is pretty simple.