Uh, on a second thought, I have the doubt that you are speaking in absolute terms - kinda gives more gains hanging or an extender. If this is your question, what I believe is that hanging can give more gains because it creates new tissue faster, due to micro-damages that the heavy weigth is causing. This means that you are using heavy weigths, so you have two problems:
a) you are approximating the injury area;
b) you are strengthening your penis, so in the long run having gains will become more and more hard.
Many hangers wouldn’t agree on what I’m saying, but this is what I think: if you want to use low tensions, basing your gains on just stretching existing tissue, extenders are the way to go; if you want to create new tissue, high-weigths hanging, manual stretching (with high-tension variations: cyclical fast stretches, fulcrum stretch) and even jelqs are the way to go. Condensed and roughly speaking.