Gemini 3.1 Pro Preview vs Claude Sonnet 5.5 vs GPT-5.3 Codex
Claude Sonnet 5.5 comes out ahead, 72 to 68 and 64 on our weighted score, and it is the cheaper option too.
GoogleGemini 3.1 Pro Preview
68/100- ECI154.8
- Price$2.00 / $12.00
- Context1.05M
- Our pick
AnthropicClaude Sonnet 5.5
72/100- ECI165.2
- Price$2.00 / $10.00
- Context1M
OpenAIGPT-5.3 Codex
64/100- ECI156.8
- Price$1.75 / $14.00
- Context400K
Claude Sonnet 5.5 is our pick
Claude Sonnet 5.5 is the better all-round choice, scoring 72/100 against Gemini 3.1 Pro Preview (68) and GPT-5.3 Codex (64). It leads on capability and price. Gemini 3.1 Pro Preview wins on inputs & features. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityClaude Sonnet 5.5Capabilities Index (ECI): Claude Sonnet 5.5 165.2 · GPT-5.3 Codex 156.8 · Gemini 3.1 Pro Preview 154.8
- Lowest priceClaude Sonnet 5.5Claude Sonnet 5.5 $4.00 · Gemini 3.1 Pro Preview $4.50 · GPT-5.3 Codex $4.81 per 1M tokens (3:1 blend)
- Longest contextGemini 3.1 Pro PreviewGemini 3.1 Pro Preview 1,048,576 · Claude Sonnet 5.5 1,000,000 · GPT-5.3 Codex 400,000 tokens
- Widest inputsGemini 3.1 Pro PreviewGemini 3.1 Pro Preview: Text, Images, PDFs, Audio, Video · Claude Sonnet 5.5: Text, Images, PDFs · GPT-5.3 Codex: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Gemini 3.1 Pro Preview | Claude Sonnet 5.5 | GPT-5.3 Codex |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 84 | 97 | 87 |
| Price | 25% | 19 | 21 | 18 |
| Inputs & features | 15% | 100 | 80 | 80 |
| Context window | 10% | 61 | 60 | 44 |
| Overall | 100% | 68/100 | 72/100 | 64/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Gemini 3.1 Pro PreviewGoogle | Claude Sonnet 5.5Anthropic | GPT-5.3 CodexOpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 154.8 | 165.2 (best) | 156.8 |
| ECI rank | #31 of 148 | #3 of 148 (best) | #18 of 148 |
| GPQA DiamondGraduate-level science questions | 94.4% | 95.6% (best) | — |
| FrontierMath Tiers 1–3Research-level mathematics | 59.7% | 88.8% (best) | — |
| OTIS Mock AIME 2024–2025Competition mathematics | 95.6% | 100% (best) | — |
| SWE-bench VerifiedFixing real GitHub issues | 75.6% (best) | — | 74.8% |
| SimpleQA VerifiedShort factual questions | 73.5% (best) | 46.5% | — |
| Price per million tokens | |||
| Input | $2.00 | $2.00 | $1.75 (best) |
| Output | $12.00 | $10.00 (best) | $14.00 |
| Cached input | $0.20 | $0.20 | $0.175 (best) |
| Blended (3:1) | $4.50 | $4.00 (best) | $4.81 |
| Long-context rate | Over 200K: $4.00 / $18.00 | Same rate | Same rate |
| Price source | Official Google API | Official Anthropic API | Official OpenAI API |
| Limits | |||
| Context window | 1,048,576 tokens (best) | 1,000,000 tokens | 400,000 tokens |
| Max output | 65,536 tokens | 128,000 tokens (best) | 128,000 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | Yes | No | No |
| Video | Yes | No | No |
| Reasoning | Yeslow · medium · high | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gemini-3.1-pro-preview | claude-sonnet-5-5 | gpt-5.3-codex |
| API providers | 26 (best) | 23 | 19 |
| Released | Feb 19, 2026 | Sep 28, 2026 | Feb 5, 2026 |
| Knowledge cutoff | Jan 2025 | Jun 2026 | Aug 31, 2025 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Gemini 3.1 Pro Preview$44.00
- Claude Sonnet 5.5$40.00
- GPT-5.3 Codex$45.50
Which should you choose?
Which is better: Gemini 3.1 Pro Preview, Claude Sonnet 5.5 or GPT-5.3 Codex?
Claude Sonnet 5.5 is the better all-round choice, scoring 72/100 against Gemini 3.1 Pro Preview (68) and GPT-5.3 Codex (64). It leads on capability and price. Gemini 3.1 Pro Preview wins on inputs & features. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Gemini 3.1 Pro Preview, Claude Sonnet 5.5 or GPT-5.3 Codex?
Claude Sonnet 5.5 is cheaper at $2.00 input / $10.00 output per million tokens (official Anthropic API price). Gemini 3.1 Pro Preview costs $2.00 input / $12.00 output per million tokens (official Google API price); GPT-5.3 Codex costs $1.75 input / $14.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $4.00 per million tokens for Claude Sonnet 5.5 versus $4.50 for Gemini 3.1 Pro Preview (1.1× as much) and $4.81 for GPT-5.3 Codex (1.2× as much).
Which scores higher on benchmarks?
Claude Sonnet 5.5 scores higher on the Capabilities Index (ECI): Claude Sonnet 5.5 165.2 (#3 of 148), GPT-5.3 Codex 156.8 (#18 of 148) and Gemini 3.1 Pro Preview 154.8 (#31 of 148). Their confidence ranges do not overlap (161.8–169.4 vs 153.5–160.8), so the gap is a real one.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Sonnet 5.5 yet, so there is no like-for-like coding score. On overall capability, Claude Sonnet 5.5 leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.
Which has the bigger context window?
Gemini 3.1 Pro Preview has the largest context window at 1,048,576 tokens, against 1,000,000 for Claude Sonnet 5.5 and 400,000 for GPT-5.3 Codex. Maximum output per response: Gemini 3.1 Pro Preview up to 65,536, Claude Sonnet 5.5 up to 128,000, GPT-5.3 Codex up to 128,000 tokens.
Which can read images, PDFs, audio or video?
Gemini 3.1 Pro Preview accepts text, images, PDFs, audio and video; Claude Sonnet 5.5 accepts text, images and PDFs; GPT-5.3 Codex accepts text, images and PDFs. Gemini 3.1 Pro Preview handles the widest range of inputs.
Are any of these open source?
No. Gemini 3.1 Pro Preview, Claude Sonnet 5.5 and GPT-5.3 Codex are proprietary and only available through APIs and apps.
Which is newer?
Claude Sonnet 5.5 is the newest, released Sep 28, 2026. Gemini 3.1 Pro Preview came out Feb 19, 2026; GPT-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: Gemini 3.1 Pro Preview Jan 2025, Claude Sonnet 5.5 Jun 2026, GPT-5.3 Codex Aug 31, 2025.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
