I think the AATBS materials are too in depth while the Psych Prep are not detailed enough. That being said more is always better so if you are going to choose one got AATBS.
I am just about to begin studying for the CPSE. I am also getting hand me down materials from both AATBS and Psychprep along with practice exams. Can you share what your experience was like, in studying for the exam viz the EPPP and the timeline you followed. Also any tips and strategies you would be able to share would be great.