Moved to MGMAT section...

I have a lot of faith in MGMAT material, but I will always argue that the best GMAT prep material comes directly from the makers of the GMAT--if your OG performance and GMATPrep performance indicate that you are doing well with RC, then I would weigh that data more heavily than any of your practice test performances.

That being said--you should still do a thorough analysis of your mistakes and try to pick apart why you get certain questions wrong.

All the best!

Yes, OG has real questions, and I agree you should always weight real questions more heavily than ones from test prep companies - but OG contains the entire range of questions, from very easy to very difficult. The "problem" you note here is simply due to comparing different sets of data.

Note that a passage itself is not considered easy or difficult. Easy and difficult questions are written for any passage. In the book, you see all of these. When you take an adaptive test, however, (whether ours or the real thing), you will ONLY see the hardest questions (assuming you're really good at verbal, of course, which it sounds like you are).

So let's say that you are given the top 20% of questions. If you limited your OG questions to only the top 20% of questions (not passages - just the hardest questions within any passage), you'd be at about 50/50 (you're getting about 10% overall wrong, and those are mostly going to fall into the top 20% of questions).

That's how the adaptive test works - when you take an adaptive test that is made to mimic the real thing (or when you just take the real thing), you should expect to get about half of the questions right and about half wrong b/c the test will cluster your questions around your ability level.