Opus 5.5 Sweeps Benchmarks Over GPT-6 Sol, Cost Remains the Debate

On September 23, Anthropic and OpenAI released their new flagship models on the same day: Claude Opus 5.5 and GPT-6 (in Sol and Astra variants). Reddit users then compiled benchmarks from various sources for a head-to-head comparison, and the community reached a highly consistent conclusion: Opus 5.5 beat both GPT-6 variants on every benchmark listed.

Confirmed

@Vast-Grapefruits compiled every benchmark they could find: Opus 5.5 leads GPT-6 Sol across the board in the table on raw scores.
@UnknownEssence put together a full benchmark comparison chart, concluding that Opus 5.5 comprehensively outperforms GPT-6 Astra and Sol, but costs more, making it better suited for quality-critical use cases.
An anomaly: on GDPval, an evaluation of "real office work," GPT-6 Sol costs only $1.06 per task, showing a clear cost advantage.

Unconfirmed

@Angaisb argued that Opus 5.5 medium isn't much pricier than GPT-6 Sol max while being stronger on nearly every benchmark, with a comparison link attached; this is a personal-opinion-style comparison, so its cost-effectiveness conclusion should be independently verified.

Why it matters

With the two leading labs launching flagships on the same day in direct competition, "quality vs. cost" became the core divide of this comparison: choose Opus 5.5 for maximum quality, while GPT-6 Sol's per-task cost is more attractive for budget-sensitive, high-throughput scenarios.

2026-09-23 ~ 2026-09-23 · 5 related posts

Primary sources

Opus 5.5 Sweeps GPT-6 Sol on Benchmarks, but Sol Runs Tasks at Half the Cost — Vast-Grapefruits · 2026-09-23 03:51 (UTC+08:00)
Full benchmark roundup: Opus 5.5 beats GPT-6 Astra and Sol at a higher cost — UnknownEssence · 2026-09-23 03:39 (UTC+08:00)

Opus 5.5 medium costs near GPT-6 Sol max but beats it on nearly every benchmark — Angaisb_ · 2026-09-23
User claims Opus 5.5 costs no more than GPT-6 Sol max yet beats it on benchmarks — Angaisb_ · 2026-09-23
[source] Full benchmark roundup: Opus 5.5 beats GPT-6 Astra and Sol at a higher cost — UnknownEssence · 2026-09-23
[source] Opus 5.5 Sweeps GPT-6 Sol on Benchmarks, but Sol Runs Tasks at Half the Cost — Vast-Grapefruits · 2026-09-23
Opus 5.5 sweeps GPT-6 Sol on every benchmark, but Sol runs tasks for $1.06 — Vast-Grapefruits · 2026-09-23