I`m an instructor with multiple agencies. I can tell you that the standards are pretty much standardized across the agencies through their membership in the RSTC. In the end it comes down to your Instructor. Some are better than others. Feel free to interview your Instructor in the same way you checked out professors in college. Except now you aren`t looking for the one with the easiest exams - rather you are looking for the one with the most experience and best personality. I can say that PADI is the most recognized worldwide and that is definately a plus. Beyond that - find an instructor you like and can work with.