Totally agree with the other posts in that a) open water standards are basically the same for most agencies and b) you should really consider the experience and reputation of the instructor as opposed to agency affiliation. As far as agencies go, PADI has a modular/ for-profit approach to teaching, which is why, (generally), you will get more out of class taught under a non-profit agency like NAUI or YMCA, which encourage their instructors to exceed standards as they see fit.

Kent
Instructor
NAUI/IANTD/CMAS