For OW & AOW, I chose the nearest LDS, which happened to be PADI, mainly because it was convenient and I didn’t know any better. I think this is typical for most new divers unless they already know an experienced diver who can help by making recommendations. when it came time for more advanced training, I was able to make a more informed decision. I went with PDIC, NSS/CDS, TDI, and NAUI for most of my more recent certs. Some of this was based on what was available locally or in the locations I traveled to, but in most cases I had a choice of at least 2 or 3 agencies for a given cert and could select the best one for the particular skill I needed to learn. (See profile if you want the low-down on what classes I took from which agency)