Yeah I know, that wasn't one of the options, but consider this: Postgres has PL/pgSQL, which is very similar to PL/SQL. (It ought to be, that's the target their working towards.) So any development done in it should be more-easily protable in the future. And the experience gained using it will be directly (or nearly so) usable on Oracle.

The big lead Oracle still has is the tools, but the underlying language is getting more similar by the month.