This is just my opinion, but, to me, the USAPL is probably the most legit organization for all the reasons you stated. Having said that, I think for your first meet it doesn't really matter. Don't go out looking to beat records or win. If you do, hey great. Go out there and get the experience. Figure out the timing of your warm-ups, the rules, how to eat during the meet, etc. In other words, just go out and have fun. Do your best, but have fun. In my limited experience in competing, I have found in the meets I've competed in that your competitors are not really your competitors. They root for you, help you out, etc. I'm not too far removed from my first meet. I was shocked at just how friendly everyone really was. I had a couple of guys kind of take me under their wing, er lats, and help me out with what I needed to do. It helped that I could actually put up some decent weight, but they were all pretty cool.
What I guess I'm saying, is go through the experience of ramping up for a meet. Read a lot and ask a lot of questions, not just here, but seek out other competitors. Go through the experience of the check-in, weigh in, where you want the racks, and equipment check (I had to run out and buy soccer socks for the DL). I learned so much from my first meet, that the experience alone was worth it.