I would say it helps a lot on Math. If you are using Dr. Collins, you'll find that his Math practice tests are very easy compare to Pearson. I'm so glad I bought 3 Pearson practice tests because I took the PCAT on September and most of my Math questions were Calculus (anti-derivative, derivative, limit and a lot of probability). For Biology and Chemistry questions are similar on the actual PCAT. If you score high on those tests, you should be fine on the actual test.
Good luck!
