I'd love to know the pass rates on CPL(H) exams and compare it with ATPL(H). Bristol publishes the CAA stats for the ATPL(A) exams, but not ATPL(H).
I have a suspicion that because the ATPL is such a well trodden route, the feedback is excellent so that for those with good memories, the exams are made that much easier for having seen the actual questions before. I further suspect that this goes some way to overcoming the disadvantage of the larger and less relevant content of the ATPL (H) syllabus over the CPL(H).
I'm not suggesting that just learning feedback is the way to go, but it certainly helps, particularly in subjects like Airlaw and AGK where the syllabus is simply too broad, and the volume of facts too large just to onboard the whole lot.