Just wondering what advantages Oracle has over Postgres? (I'm skeptical, but I honestly don't know.)

We chose Postgres over MySQL by a very fine margin, but we're pleased we did. Seems to have fewer "try to make your life easier but end up doing the opposite" quirks.

The optimizer is smarter and it's better at concurrency control. You'll get better performance out of Oracle when you have very-long-running transactions or lots of transactions at once operating on the same tables. The former isn't a concern for most web applications, but the latter might be.

The above is received wisdom from academics, though, so it may be dated. PostgreSQL has improved a lot in recent years.

And if you want nearly everything Oracle has to offer at a fraction of the price, consider EnterpriseDB.