Model Comparison
Gemini 2.5 Flash Preview (Sep '25) (Reasoning)
vs. GPT-5.5 (high)
Comparing 2 AI models · 10 benchmarks · Google, OpenAI
Recommended Pick
Op GPT-5.5 (high) 11 metric wins Strongest on: Throughput, Reasoning, Intelligence
Lowest Price
Gemini 2.5 Flash Preview (Sep '25) (Reasoning)
$0.00/1M input price
Best Reasoning
GPT-5.5 (high)
63.1 reasoning score
Blends available reasoning benchmarks
Best for Coding
GPT-5.5 (high)
58.5 coding index
Composite Indices
Higher is better; speed and price are normalized
Standard Benchmarks
Only benchmarks with data are shown
Differences That Matter
Price gap
Gemini 2.5 Flash Preview (Sep '25) (Reasoning) is ∞x cheaper on input tokens than GPT-5.5 (high).
Reasoning gap
GPT-5.5 (high) leads Gemini 2.5 Flash Preview (Sep '25) (Reasoning) by 8.6 points on reasoning.
Coding gap
GPT-5.5 (high) leads Gemini 2.5 Flash Preview (Sep '25) (Reasoning) by 33.9 points on coding.
Top-pick rationale
GPT-5.5 (high) wins 11 measurable categories, including Throughput, Reasoning, Intelligence, Coding.
Response Face-Off
Run one prompt through the selected models and compare response quality with live speed and cost context.
Gemini 2.5 Flash Preview (Sep '25) (Reasoning)
TTFT
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Time
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tok/s
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Tokens
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Cost
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GPT-5.5 (high)
OpenAI
TTFT
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Time
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tok/s
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Tokens
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Cost
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Which answer was more useful?
Full Comparison
| Metric | Go Gemini 2.5 Flash Preview (Sep '25) (Reasoning) | Top Pick Op GPT-5.5 (high) |
|---|---|---|
| Pricing per 1M tokens | ||
| Input Cost | $0.00/1M | $5.00/1M |
| Output Cost | $0.00/1M | $30.00/1M |
| Blended (3:1) | — | $11.25/1M |
| Specifications | ||
| Organization | OpenAI | |
| Release Date | Sep 25, 2025 | Apr 23, 2026 |
| Performance & Speed | ||
| Throughput | — | 53.8 tok/s |
| TTFT | — | 15266ms |
| Latency | — | 15266ms |
| Composite Indices | ||
| Value Score | — | 100.0 |
| Reasoning Score | 54.5 | 63.1 |
| Intelligence | 23.8 | 53.1 |
| Coding | 24.6 | 58.5 |
| Math | 78.3 | — |
| Standard Benchmarks | ||
| GPQA | 79.3% | 93.2% |
| MMLU Pro | 84.2% | — |
| HLE | 12.7% | 43.0% |
| LiveCodeBench | 71.3% | — |
| AIME 2025 | 78.3% | — |
| SciCode | 40.5% | 55.9% |
| LCR | 64.3% | 73.3% |
| IFBench | 52.3% | 71.6% |
| TAU-bench v2 | 45.6% | 93.0% |
| TerminalBench Hard | 16.7% | 59.8% |
Key Takeaways
Gemini 2.5 Flash Preview (Sep '25) (Reasoning) offers the best value at $0.00/1M, making it ideal for high-volume applications and cost-conscious projects.
GPT-5.5 (high) has the strongest reasoning profile with a 63.1 reasoning score, combining the available reasoning-heavy benchmarks.
GPT-5.5 (high) reaches a 58.5 coding index, making it the top choice for software development and code generation tasks.
All models support context windows of ∞+ tokens, suitable for processing lengthy documents and maintaining extended conversations.
When to Choose Each Model
Gemini 2.5 Flash Preview (Sep '25) (Reasoning)
- Cost-sensitive applications
- High-volume processing
GPT-5.5 (high)
- Complex reasoning tasks
- Research & analysis
- Code generation
- Software development
