I used both of these materials.Knewton
really made the difference for me.
For verbal, Knewton
is amazing. MGMAT verbal books are good as well (esp sentence correction). However, it goes into so much detail that it can sometimes be overkill imo.
If you watch all of the Knewton
videos, lessons, tests, etc. you're going to find it difficult to ALSO go through all the MGMAT guides
unless you have several months at your disposal. I would recommend using them as supplement material for things you want more details about.
For quant, Knewton
was also very good. It bumped me from a 44 to a 47. It doesn't cover the more complex material in nearly as much detail as MGMAT. However, it does cover the fundamental material with great clarity. So again, I would recommend using MGMAT as supplementary material.