I took the AUD section using Becker twice and scored in the 60's. Then, I added the Ninja MCQ's and mostly used it to practice the SIMS because that is the portion of the exam I was very weak on. I trended about 80% on Ninja. My score went up from a 69 to a 91. I definitely recommend! I do think that the Ninja MCQ tend to be difficult on certain topics.
I had also purchased the AUD Final Review from Becker, and used it just for the extra MCQ practice (and paid $$$$)