Honestly - It is in your opinion.
To me a reputable breeder isn't just someone who does well in shows or is considered good by others, it is someone who breeds to the SOP ( so get the Standard of Perfection and research your breed well! ) but ALSO cares for, raises, and breeds their poultry with respect. Someone who doesn't just have them in cages or small runs, someone who feeds them more than just wheat, corn, and soy, and someone who's willing to explain how they do their own process, or how they feel the breeding should be done, and what they feel are flaws and great aspects of their flock or individual birds. Someone who has background knowledge on the bird, and someone who doesn't ruin the breed by turning it away from its origin.