I've been rxed benzos now for a couple years, and I can tell you I've tried many many different kinds (mostly prescribed but also ones illegal in the US). Honestly, klonopin and ativan have worked the best for me. Klonopin is great for the whole day, or half the day depending on how bad your disorder is. And ativan is amazing for getting rid of those panic attacks that are just waiting to happen. But you have to remember we are all chemically different, and will respond to different drugs differently.
Personally I think xanax is shit, and didn't do anything except make me want to eat ten bars a day, so instead I just got rid of them. I'm just now figuring out though that my anxiety is more linked to my supposed 'bi-polar' and from what I believe, my ADD. Getting yourself healthy really helps a lot, and you may find your panic disorder is caused from another disorder, which can be helped without the use of benzos. Because as much fun as you think being prescribed benzos is, it's not. You will be dependent on them, and if you run out early for some reason (bad month more attacks then usual) you go through hell if you start to withdrawl. Lucky enough my pharmacy would always give me enough to last me until my next doctors visit, which is pretty unheard of.