If you're using SQLite 3, the TEXT type stores data UTF encoded, while the BLOB type stores it raw. BLOB is more geared toward binary data storage.
If you're really concerned about problems due to UTF encoding, use a BLOB. It looks like Storable deals with UTF8 fine, but I don't know how much it likes UTF16. Since Storable generates a string, I would probably store it as a text column.
If you're using SQLite 2, all the datatypes are really strings. You could declare the column as an INTEGER and it wouldn't care.
I would still pick TEXT, because it describes the data the best.
Edit: I misread the Storable docs. See below for details.