We have two separate things to discuss: how the test feels to you and what score you get.
This is all anecdotal: I have heard from a number of students over the years who feel that the GMATPrep quant is easier and that our quant is harder. I have also heard from a number of people who think that the GPrep quant is closer to the real thing—but an equal number have said that our quant is closer to the real thing (though often still harder than the real thing).
I think this depends mostly on someone's quant level. The question pool (number of questions) in GPrep is shallower, so the higher you go, the harder it is for the software to give you lots of really hard questions. Our tests have more problems, so we can keep pushing you, even at really high levels.
This happens somewhat on V as well, but most people talk about really noticing it on Q.
We also have a goal in general of trying to "overprep" our students. The last thing we want to do is have you think the real test is harder than what you practiced. Ideally, you feel the real test is either about the same or easier.
Now, having said that, we do adjust for this in the actual scoring—so our scoring is as accurate as we can make it. (The real test has a standard deviation of about 30 points; our standard deviation is about 50 points.)
Next, large score fluctuations often indicate issues with timing and executive reasoning decisions. If you are having these issues, then you will struggle more on our test than on GPrep—and you will likely also struggle more on the real test. You know that practice tests don't count. You know that the real test does. The more the practice test can find ways to put you under increased stress (despite the fact that you know it doesn't really count), the more it will simulate the real test—and show you possible weaknesses that you want to fix before you get into the real test. Read this:
http://tinyurl.com/executivereasoningGo back and review your exams—is this part of the problem? Were you sometimes getting really stubborn and hanging onto a problem for far too long—and then having to rush later in the section? Or were you artificially rushing because you were worried that you would get hung up on something and then finished far too early? That kind of thing.
If so, start here:
https://www.manhattanprep.com/gmat/blog ... -the-gmat/If this is an issue for you, you'll want to learn how to incorporate those ideas into your studies and your test-taking so that you don't risk a possible swing in the downward direction on the real test.
Finally, I should just mention: It's important to make sure that you are taking the whole practice test under official testing conditions in order to get the best data. (This is especially true if you take the test under the original order: Essay, IR, Q, V.)