What body of Freemasons is most esoteric in nature?

Answer 1

I assume you mean a comparison between (Ancient) Free & Accepted Masons (sometimes called "masculine" or "mainstream") and Co-Masonry (co-ed). They are about the same. You will find it easier to find (A)F&AM lodges in the world, but women cannot join. Once you choose one of the two types, you cannot switch back and forth and cannot visit the other's lodges.