Also check out the boards at Pedal-on.com. It's a spinning board and there are people there from different certs and you might glean some neutral info. I was certified in Mad Dogg, and although I agree with Jen, they don't teach you how to teach, if you have the talent already, I much prefer to make my wn music and choreograph my own routines. Not my career, but as a cyclist, it's "my thing", and I focus alot of time on it, and studied other good and great instructors. I've also committed to continuing education as well to go beyond just teaching and developing programs for my students such as heart rate training. So again, it depends on how much work you prefer to independently put in, and yes, it all has a cost.

You might see which club you'd like to teach at and see what certs they take, as someone else mentioned, some only take certain ones. The club I taught at only accepted Johnny G/Mad Dogg...otherwise legally they could not call it "Spinning" (trademarked by Mad Dogg) they had to call it indoor cycling and that doesn't have the same appeal to people.

Good luck on your decision!