The Complete Manual of Suicide - Japanese book first published on July 93 and sold more than 1 million copies, providing matter-of-fact assessment of each method
There are more modern, and updated references. Final exit international publishes a ebook surveying methods, and has a community for helping prepare for the transition. wiki
A community with more active information being updated bimonthly is Peaceful Pill (wiki)
Exit (Peaceful Pill) has a large support organization and active forums for members. They often do webinars talking about end of life planning, estate planning, insurance, etc.
Both organizations charge a small fee for the ebooks but you can easily find it on the high seas (fmhy/LibGen)
But to answer your question about winners, Nitrogen displacement, and Nembutal appear to be the most favored.
Nitrogen asphyxiation is some scary stuff. You just die without realizing there is a problem. It's a problem in confined spaces in industrial environments.