BLOBs or references in PostgreSQL
I think you should store the data in the database as a normal bytea column.  That way you get all the advantages of a database, and you can process the data using database functions (and even PL/Python, if you want that).  Larger data items will automatically be stored out of line, so there would be no reason for you to introduce another reference indirection.

The main reasons for storing large binary objects outside the database would be if they are too large to be able to store and retrieve them in a satisfactory time, if they bloat the database beyond practicality, or if you need to access the files as files from a separate application.  None of that applies there, as far as I can tell.