I’ll be honest, I can’t say that I truly understand the "this agency vs. that agency" avenue. I believe the relevance is more about what quality instructor you are involved with. The agencies all have the same general intent/teaching paths, but the instructor can stress and control the topics/focus of the whole class/certification. The instructor makes or breaks the class, and instills many peoples first experience of scuba with whatever they say/do in class which is more important for a new diver than what agency the instructor is hired by.