I'm PADI. I have 7 "official" buddies/friends that I would trust my life with and who are very skilled divers. 2 are PADI, 1 is NAUI, 2 are SSI, 1 is ACUC and 1 is PDIC. We all had really good instructors and we all take the sport seriously. That being said, sure we have certain differences of opinion when it comes to certain things but who doesn't. Whatever you decide, choose a good instructor (talk to the various instructors and try to gain a sense of how they would teach), take your training seriously, always try to learn more than what is "required" (at least knowledge wise) and have fun!