I wanted to share my experience: I have written quite a few CAT-s and my scores were more or less the same. For Kaplan users, have in mind, QUANT section is easier than on the actual test, while verbal is rather hard and some problems are of low quality (especially reading is frustrating).
As for
MGMAT - Quant section is very hard
I really recommend Veritas tests, I guess overall they are the best representatives of real tests.
And here are results for each test:
CAT Total % Quantitive Verbal IR
GMATprep 700 90 46 71 40 90 7 81
KaplanTest 740 97 51 97 34 71 3 25
KaplanTest 710 92 50 88 36 81 4 37
KaplanTest 730 96 51 97 35 76 6 67
KaplanTest 710 92 50 88 38 85 4 37
KaplanTest 730 96 50 88 40 91 7 81
GMATprep 720 94 48 78 41 93 8 92
VeritasTest 720 94 49 83 40 90 5 52
MGMATTest 690 87 48 74 36 81 2.96
VeritasTest 740 97 50 90 41 93 6 67
VeritasTest 740 97 50 90 42 96 6 67
actualTest 720 94 49 79 39 89 4 37