As this is an Oracle forum we have to say that Oracle is superior to any other RDBMS so you should always use it instead of other products.
However, we cannot give an answer as to which is best for you as there are so many factors involved and it depends on the functionality you need from Oracle compared to what you have with MySQL.
One thing to consider is licensing. You haven't said which MySQL version you are using but I am guessing it is the 'free' version. If you decide to use Oracle you will need to pay a license fee as there is no free version.