Across 28 shared benchmarks, GLM 5.3 Flash scores higher on 13 and GPT-5.5 on 15. The widest gap is OmniScience Non-Hallucination, where GLM 5.3 Flash scores 72.4 against 12. GLM 5.3 Flash is the cheaper of the two on tracked API pricing ($0.15 against $5.00 per million input tokens).
Best tracked score per model per benchmark (default configuration; source-attributed). ↓ marks lower-is-better metrics. Open either model for its full surface, provenance and pricing. Quoted rates are the price-setter row we currently track for each model — its direct or vendor-official listing where one exists (direct, direct), otherwise the lowest tracked offer.