Here is how I saw it:
The NCEES one I thought represented the test the best, but their answers are not explained well so that you understand what is actually happening in the problem.
The Complex Imaginary tests are well worth the money and have very well done explanation of the answers. The downside of these tests are that each test seems to be a copy of each of the previous tests.
The Spin Up tests were good, albeit some errors and not necessarily good answer explanations, but they also covered stuff that I felt would never be on the test. It was not just one question, but like 12 in a row on each test. Having said that, I would recommend the test for the one reason is that while the questions are not trick questions, they will teach you to read and comprehend the whole question before starting to work. This was a problem of mine. I missed a many questions on the Spin Up tests because I went too fast and solved for the wrong item.
The Camara sample examinations were good practice, but like the practice problems, many of the questions seemed above what you'd expect on the test.
The Electrical Engineer's Guide to Passing the Power PE Exam is a better reference book than test. The first half of the book is a great reference source. The second half contains one test that is fraught with errors.
The Complex Imaginary, Spin Up, and NCEES tests were the ones I felt I learned the most from. That was 10 tests to cycle through so that I would be able to take the test again at a far enough span of time that I did not remember the problems and just attempted to solve them.
I did not get the Kaplan so I cannot comment on it.