I had taken both and passed. When I told my PMP course mate that CITPM was not easy he kind of smirked. Last I checked with him he had not attempted the exam yet.
You definitely need to put in the time to go through the text and have some level of understanding of the topics. CITPM has MCQ and written papers, and there is not much time to answer the questions.
For PMP some have commented that it is a test of your understanding of the English language. The questions aren't technically difficult, but it tests your understanding of the topics, and how well you grasp the question. So depending on how "correct" you interpret the question or scenario, will determine if you select the correct answer. Frankly some of the model answers were debatable, that is why attending the prep course is important. If the instructor is good, he should explain how to read the questions and answer according to PMBOK context.