Hi cliveo,
The scoring algorithm on the Official GMAT is far more complicated than most people realize. Since that algorithm is proprietary, no GMAT company has an exact match for it, thus CAT scores can vary a bit based on the 'biases' involved in their respective designs. Keep in mind that the accuracy of CAT results also depends heavily on how YOU choose to take the CATs. The more realistic and 'test-like' you make those experiences, the more likely the score results are to be accurate. If you deviate from the standard Test Day 'event' (skipping sections, pausing the CAT, taking it at home, taking it at a different time of day from your Official Test time, etc.), your scores can deviate too. The
MGMAT CATs are generally regarded as bit harder than the Official GMAT, but they'll still give you a reasonably accurate score result (assuming you use those CATs properly). The GMAC CATs are the most realistic CATs on the market, but each comes with a much smaller pool of questions than what you will face on the Official GMAT.
From what you've described, it sounds like you have not done much in the way of organized study for the Verbal section. To raise your Verbal Scaled Score to a V40+, you'll likely need to invest in some new practice materials and learn/practice some new Tactics.
1) What is your overall score goal?
2) When are you planning to apply to Business School?
GMAT assassins aren't born, they're made,
Rich