If I had to choose, I'd be an AU over a joint user. If anything went south, then I could remove my self easily. As a joint user, you can't do that. Score-wise, there is no difference per FICO. Under a manual review, there should be no difference, though I am not sure how they'd look at it in terms of DTI. I suppose more favorable than a joint user.

You should have been added as a joint user if your name was on the app at the very day they applied for it. You cannot be added as a joint user after the app was submitted.