Hi MikaelD,
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. The most realistic CATs available are the 6 from GMAC (the 2 free CATs, and each of the 2 that come with Exam Pack 1 and Exam Pack 2), but the
MGMAT CATs will provide you with a reasonably accurate score (when used correctly).
It's important to remember that he 'accuracy' of a CAT score is also based on how realistic YOU choose to make the CAT-taking process. If you skip sections, pause the Test, take it at home, take it at a different time of day as your Official GMAT, do anything else that is unrealistic, etc., then your score is likely to be less accurate. All of that having been said, these recent CAT scores are fairly close to your Official Score, so unless you have additional evidence to the contrary, then we have to assume that they're accurate.
A 690 is a fantastic score (it's just a bit shy of the 90th percentile overall), so it could be enough to get you into your first-choice School. As such, a retest might not be necessary. Depending on the Schools that you plan to apply to, you would likely find it beneficial to speak with an Admissions Expert about your overall profile. There's a Forum full of them here:
ask-admission-consultants-124/1) What is your goal score?
2) When are you planning to retake the GMAT?
3) When are you planning to apply to Business School?
4) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich