To answer why Scrappy is so popular, it's probably because when Being A DIK first came out, Scrappy was the first mod for it and has since kept up to date with the game. When I first downloaded the game years ago, I played it basically vanilla (vanilla =/= meaning without mods), and then I searched for a mod that would highlight story pathing choices, Scrappy was literally the first mod on the scene. I'm not at all familiar with SanchoMOD so for myself the simplest explanation comes at the level of which one to trust and which one is unneccesary. If they're both doing virtually the same thing, even if SanchoMOD has an improved-looking UI, then it don't matter.