I don't really understand how that's the case. In 15 years as a professional DBA working with both Oracle and MySQL I have never found myself in the position of thinking, hmm, Oracle or MySQL for this project? It just doesn't really happen (no matter how much Monty would like to believe it does). I recently decided between MySQL and SQLite on a smaller project (SQLite won that one). I can see myself deciding between Oracle and Postgres one day (never happened in practice).
