Correct Looks Better: Pairwise Comparisons Reveal Accuracy Rankings

This research explores whether pairwise comparisons used to rank generative models actually reflect ground-truth accuracy. By converting multiple benchmarks into free-form formats, the authors found that Elo-style rankings achieve a remarkably high correlation with objective correctness. Surprisingly, this alignment remains strong even when the judge model is weaker than the candidates it evaluates, outperforming direct grading methods. While critics often worry about judge biases or stylistic cues, the study demonstrates that these factors have a minimal impact on the final model hierarchy. Furthermore, the paper identifies "echo"—or repetitive output—as a key reason why judges prefer one answer over another when both are technically correct. Ultimately, the results suggest that relative preferences are a robust and reliable proxy for absolute accuracy in competitive model evaluation.