We now support storing document in the app’s internal storage area (where things have been stored historically) or an external location of the users choosing.
There’s one big upside of external storage, and number of downsides.
First the upside, if you have large documents and limited internal storage, but have a large SD card, external may work well for you.
However:
External is slower.  This mostly an issue during import.
If you ever switch back to internal, the external documents will be lost.  Internal documents are always available.
When the app is uninstalled or the storage is cleared, the internal storage is cleared, the external storage is not.