As in any form of fitness instruction it isn’t the cert that matters. What is important is what you do to further your education and understanding of fitness and fitness instruction. I recommend to students that they seriously consider if they truly want to be instructors or if they just want a paycheck. Fitness can be a very rewarding career, but loving what you do and yearning to improve your knowledge, skills, and abilities will make a good instructor into a great instructor.
I have had certs from a number of organizations. For some, I took the course to see how they handled the topic(s) and the test to be able to provide advice (short of actual questions and answers) to students preparing to take the cert exam. I have not reviewed an NCCA accredited organization that didn’t do a good job of providing responsible information and fair testing procedures. But definitely go for something NCCA accredited.
I am personally partial to ACE. I currently have an ACE Group Fitness Instructor cert, an ACSM Personal Trainer cert, and several specialty certs. I teach students for certification and CECs on the Big Island of Hawaii. If you are interested, go to www.hawaiifitnessacademy.com for more information. The site isn’t finished, but it is up.