The Tibetan histories say Kamalasila won and the emperor ruled for the Indian gradual path. A Chinese document recovered from the sealed cave library at Dunhuang says Moheyan won and the emperor ruled for him. Both are partisan, both are the only substantial account their side left, and they cannot both be describing the same outcome.
Paul Demieville edited the Chinese material in 1952 and made the problem impossible to ignore. Before that the Tibetan version stood more or less alone in Western scholarship, as it had stood alone in Tibet, and the debate was told as a clean victory. Afterwards it became a case study in what happens when a tradition's founding story is checked against a source the tradition did not control.
Later work has pushed further and questioned the frame rather than the verdict. There may have been no single staged debate at all. What the evidence supports more easily is an exchange of written positions over a period, submitted to a court that eventually made a policy decision, which the tradition later shaped into a contest between two champions in a hall because that is a story that can be told.
The atlas records both accounts and does not choose. What is not uncertain is the use the story was put to. Whatever happened at Samye, the narrative of an Indian master defeating a Chinese one became the charter for Tibetan Buddhism's orientation, and it was still being told for that purpose a thousand years later.