Disclaimer: I have the PCAT destroyer, Dr. Collins and the Pearson practice exams.
The Pearson practice exams are great because they give you a composite score, as well as an individual section score. IMO, they give you an accurate idea about the types of questions that you'll see on the exam. IMO, they are a great study tool and imperative for the exam.
I like using Dr. Collins' study material since they are divided up into practice exams and I've seen some of the questions from these exams on the Pearson practice exams. The review guides that come with Dr. Collins' material are helpful, but the best attribute (again, IMO) are his practice exams. Tons of questions, although the explanations regarding the questions (especially for Chemistry) are lacking. However, I can definitely understand why his study materials are so popular.
Some people rave about the PCAT destroyer, however, I'm not a huge fan. (Truth be told, I wish that I hadn't purchased the material.) I think that there are tons of questions, however, I don't feel that they are all that indicative about the material covered on the exam. Furthermore, there is neither verbal nor reading comprehension materials with his study section. I think that he emphasizes the Organic Chemistry section, however, there aren't many Orgo questions on the exam and his questions are more difficult than those on the real exam. Finally, his study guide is just questions ... No review material at all.
Again, I think that it's all about preference. I think that the Dr. Collins' material is great. I think that the Pearson practice exams are necessary. I don't think that the PCAT Destroyer is all that helpful, but YMMV.