If you want to go be pedantic about it and select one metric, markets are evaluated on their Brier Score or some other Proper Scoring Rule, not accuracy.

However, I prefer calibration as a high level way to explain prediction market performance to people, as it’s more intuitive.

Edit: just found the answer myself: “accuracy measures the percentage of correct predictions out of total predictions, while calibration assesses whether a prediction market's assigned probabilities align with the actual observed frequency of those outcomes”