Maybe things have changed since I studied which was less than a year ago. Regular Manhattan GMAT
lowballs your score, but their CAT's are a little off and inflate your score. But their questions are on target.
The PR quant is too easy, but punishes incorrect answers. Their verbal is on par. Kaplan
CATs are wrong. Their questions, though they may look like gmat questions, do a very poor job of imitating gmat questions. Their testing is all wrong and off whack. I scored a 580 about two weeks before I scored a 730 on official exam. Nobody will tell you that Kaplan
exams are good.
Again, nothing beats the GMATPrep. It's like a cheat to take the actual GMAT before you really do so. Save them until you're ready.
does not have their "regular" paper tests anymore (I think that's what you were referring to). As far as accuracy of their CATs goes, I think that MGMAT used to use Cambridge CATs in the past, while developing their own scoring algorithm. Nowadays, you can take 6 MGMAT tests online. It seems that Manhattan's verbal questions are on par with GMATPrep material, while math questions tend to be on the more time-consuming side, making it difficult to finish the quant part on time. Overall, based on the preliminary data MGMAT received from the students, actual GMATPrep scores tend to be 10 point higher than what students get on the MGMAT practice test. To me, 10 pt margin of error is pretty good!
To you point: THERE IS NOTHING OUT THERE AS GOOD AS GMATPREP!