You're thinking of this as "getting hired" by a gym, as opposed to getting hired by a client. If you want to make $10/hour setting pins in a commercial gym, any of those certifications will allow you to get PT insurance, which is the real object of the requirement. But trust me when I tell you that nobody hires a trainer because they possess the coveted CSCS certification, cheerfully provided to all graduating PE majors by the NSCA. We asked them, and they told us that nobody has ever called any of them for their services as trainers because they have the CSCS. On the other hand, our SSCs get called every week by clients wanting to hire them to teach the SS method.
Your thinking about this wrong too. Anybody care to explain it to him?