- You work with external (non-managed) media for your Libraries
- Or you work with managed media and all your Libraries reside on the same drive
When you work with external media for your Libraries, or you work with managed media and all your Libraries reside on the same drive, you can easily use media from one Library for Projects in any other Library without creating physical duplicates of the media.
Then only possible drawback you can get is if you ever need to search for specific clips across different Libraries. You can only search inside one Library at a time.
I work with one library per project. And I pull footage from other libraries all the time. If you do this, you definitely want to consider using external media. Once they got rid of the stupid warning dialogue when you edit media between libraries it got a whole lot easier.
It also helps projects load faster and remain more nimble when you're working with them since there is less media and thumbnails FCP X has to load.