When people say easy or hard, it's all based on their own knowledge. If the question in Pearson that wasn't in Collins study guide, they could get it correct for a reason that they have some background. It's really hard to judge.
I would defined say Pearson is more similar than Kaplan, and more close to what pcat look like.
Pay attention!!! I didn't say it's the same! It's similar on the "strength" of the question. No matter how much I studied, my background knowledge, practicing Preston and Collins.. Still didn't help to improve Kaplan practice.. Eventually I gave up.. I found Kaplan to be rediculously detailed..
No matter how much I studied I still got low on Kaplan consistently. Finally I put it away, cause it gave me zero knowledge.
If you got wrong in Pearson, look up the answer and study it.