I did cliff's test prep, kaplan and "top score for the pcat" cd. I would say the cliff's test prep was good prep but it is important to do as many and as much prep as you can (I'm sure you know that).
The reading comprehension was so hard on the real test!!! Way harder than the cliff's test prep. but keep in mind that I consider myself not very good at reading comp sections.
So, kaplan reading comp was about the same as the real test.
Cliff's math was about the same as the real test (but remember, there is no geometry on the pcat).
Cliff's chem was about the same as the real test.
Cliff's bio was about the same (maybe a little easier).
Practice writing as much as possible! I got a 96 overall but did not do well on the writing.
I think in general, kaplan is usually thought of as harder than the real test and I would say that is true but kaplan is not extremely harder, jsut a little harder. Top score for the pcat is hard but a good review because they have a timer!
So, if you're breezing through cliff's review, that's a good thing. Now you can practice using a timer, practice writing a lot!, reading comprehension is hard.