Freeze before sous vide or sous vide, defrost then sous vide
This could work either way, and in part, depends on how you like to prepare them.  Since you would likely cook them low temp for a long time to take advantage of the cooking technique, I would marinate or brine (your preferred preparation),sous vide, then freeze.  That way, you would only have to thaw (or re-therm in bath) and finish (sear of some sort) to have a meal ready in less time than the original preparation