GCG and Chanca piedra are equally great. I´ve used both and can teel they worked out for me. However, we must keep in mind that both GCG and Chanca piedra are "supporting actors" as what really works miracles is to flush. GCG or CP as well as a bile mover such as Chinese Bitters or Artichoke tincture help a lot but nothing beats the effect of a good liver flush.
Good luck and remember to be patient and persistent.