I think the big issue of the PADI cavern certification is how instructors are made. At one time (and could still be) inorder to be a PADI cavern instructor the only requirement was be a PADI instructor,hold an intro cert,proof of 25 (?) cave dives at that level,and pay the fee to PADI to teach the course. NSS-CDS and NACD require instructors to be full cave,completed 100 cave dives,and go through intership with an instructor institute. Does all this guarantee one cavern instructor is better than another-No,but if presented with the same credentials who would you chose.