I completely agree with above comments. I have my masters in Exercise Physiology and hold my CSCS certification. I took the ACE exam while in undergrad and did not need to study to pass. Very basic knowledge and I had already taken a few related courses in college. I'm currently in the process of "studying" for the NASM PES exam which has been changed to NASM CSPC to include more content. I'm going to take both exams. I thought the NASM tests would be more demanding and would provide deeper knowledge of physiology as well but they do not. It's been 10+ years since I've been in college and only 4 weeks into the "purchase" of the NASM testing bundle and I took the practice PES exam (in 45 min.) and passed with an 80% score. I've only read the first 4 chapters of the book. I'm very disappointed it is not more comprehensive. The CSCS requires the most understanding and was by far more difficult than NASM PES, and ACE. I have heard good things about ACSM and will pursue that certification next.
Rating
CSCS by: Rob
I've obtained all 3, and while ACSM and NASM are solid, the NSCA-CSCS is the gold standard. It was definately the harder of the 3 exams, requiring a more comprehensive knowledge of biology, biomechanics, A&P, and kinesiology. While I believe the other 2 might know their stuff, the CSCS WILL know their stuff!
Rating
NSCA CSCS or NASM PES by: MD
Due to how long the CSCS has been around it is regarded as the standard. Not because it is better but because it has been around for nearly 30 years. I am NSCA CPT and NASM PES certified. It comes down to what you want to do. If you want a job as a strength and conditionsing coach you'll need the CSCS since there is a bias towards that certification. However, there is only a difference of 4 or 5 chapters beween the NSCA CPT book and the NSCA CSCS book. So once I realized that I went for the NASM PES since it was new information for me. Both are good and the difficulty of the test depends on your background education wise. My goal is to have both so I'll be taking the CSCS next.