From my understanding there is a difference. However, I am not sure how much of a difference there is. I am sure someone else on the Forum can answer that.
I just wanted to give my opinion on something. You should not pay the collection until they agree to a PFD. You probably will not be able to settle for less and get this option, but I wish so much that I would have done this in my past. You have leverage now, since you have something they want (money). If you pay, then they will more than likely not be as willing to work with you.
Just my thought. Good luck.