I always used Boudreaux's as a barrier ointment. It's my favorite for my baby's sensitive skin. However, if she does get a rash I immediately begin to apply this maximum strength because it helps the rash better in my opinion.
I have used both products and I like Desitin better. I feel that Desitin goes on smoothr making it easier to coat the diaper rash. In my opinion, Desitin does a better job of clearing up the diaper rash and it smells better too!