Notabilia has visualized the hundred longest discussion threads at Wikipedia that resulted in the deletion of an article and the hundred that did not. The visualized threads take on shapes depending on whether the discussion was controversial, swinging, or unanimous. For those whose brains can process visualized information (as mine cannot), you will undoubtedly learn much. For the rest of us: Oooooh, pretty!
They’ve posted some other analyses as well. For example, “The analysis [pdf] of a large sample of AfD discussions (200K discussions that took place between November 2002 and July 2010) suggests that the largest part of these discussions ends after only a few recommendations are expressed.” And: “Delete decisions tend to be fairly unanimous. In contrast, we found many Keep decisions resulting from a discussion that leaned towards deletion…”