I have signed up for the Knewton GMAT course because it was cheaper than the MGMAT course, so I had access to the 6 Knewton CATs that they now offer. After I finished the 6 CATS from Knewton, I went ahead and purchased MGMAT's 6 CATs online for further practice, and this is what I think about Knewton and MGMAT CATs:
MGMAT CATs are far superior to Knewton CATs. This does not mean the Knewton GMAT course is worse than MGMAT's, since I have not taken the MGMAT course. And in fact, I did enjoy the Knewton course. It was very helpful, with plenty of practice problems and such to help me prepare for the GMAT test.
But this thread isn't about the course lol. I felt MGMAT CATs were superior because over the 6 CATs I took, I believe my scores were logical based off the number and types (difficulty) of questions I got right or wrong. I never doubted the scores that MGMAT showed me because they honestly made sense. Also, the detailed report they provide for each test taken is phenomenal! They provide the time it took to answer each question, the overall time passed while I was on a certain question, and the biggest help for me, the DIFFICULTY of each question. Also, the explanations were simply amazing.
Contrasting this with the CATs from Knewton, I was sorely disappointed. Of course, I did take the Knewton CATs before MGMATs, and the first 3 exams, I didn't realize the algorithm that Knewton uses is flawed. But by the 4th and 5th CATs, it became painfully apparent. Although the questions in Knewton were sufficiently difficult, with a wide variety of question types, the end result was much to be desired. Normally, how the GMAT CAT works is that if you answer a question right, the next question is more difficult, and if you answer a question wrong, the next question is easier. Also, answering easier questions wrong count more against you than answering difficult questions wrong. Now, most of the questions I answered wrong on the 5th CAT were easy ones (about 8 in quants, and 7 in verbal). Ok fine, so my score should be lower due to this fact. But where I have an issue with Knewton's CATs is the fact that I was still getting "easy" questions after getting 7, 8, or 9 questions right in a row. That is the fundamental flaw in Knewton's CATs.
Well, enough with my rant.. if you read this then great, but if u didn't read the whole ESSAY (lol), then my main point is... I STRONGLY recommend MGMAT CATs over Knewton CATs!