Reference selectors and Enumeration dropdowns are interchangeable for most functionality but you shouldn't use them together, if you want to give users a preset choice you should use a dropdown widget - as Paul mentioned.
You can use reference selectors to create a user made selection for a drop-down, but you should use a string attribute instead of an enumeration so users can add more options, and you have to create the objects before they become available.
Hope this helps
Ah yes, thank you both. I have it working now.