Google: Gemini 2.5 Flash vs Google: Gemini 3.1 Pro Preview Custom Tools: Which AI Model Is Better?
Updated March 24, 2026· Based on independent benchmark data
Quick Verdict
Google: Gemini 3.1 Pro Preview Custom Tools leads in intelligence with a score of 57.2 vs 19.4. Google: Gemini 2.5 Flash is 6.7x cheaper at $0.30/1M tokens vs $2.00/1M. For speed, Google: Gemini 2.5 Flash wins at 343 tok/s vs 117 tok/s.
Head-to-Head Comparison
| Metric | Google: Gemini 2.5 Flash | Google: Gemini 3.1 Pro Preview Custom Tools |
|---|---|---|
| Intelligence Score | 19.4 | 57.2 |
| Coding Score | 14.5 | 55.5 |
| Math Score | 46.7 | N/A |
| Speed (tok/s) | 343 tok/s | 117 tok/s |
| Latency (TTFT) | 0.31s | 21.91s |
| Input Price / 1M tokens | $0.30 | $2.00 |
| Output Price / 1M tokens | $2.50 | $12 |
| Context Window | 1.0M | 1.0M |
| Max Output Tokens | 66K | 66K |
| Input Modalities | File + Image + Text + Audio + Video | Text + Audio + Image + Video + File |
| Output Modalities | Text | Text |
| Free Tier | No | No |
Detailed Analysis
Intelligence & Quality
Google: Gemini 3.1 Pro Preview Custom Tools outperforms Google: Gemini 2.5 Flash on the Artificial Analysis intelligence index with a score of 57.2 compared to 19.4. For coding tasks, Google: Gemini 3.1 Pro Preview Custom Tools has the edge with a coding score of 55.5 vs 14.5.
Speed & Latency
Google: Gemini 2.5 Flash generates output significantly faster at 343 tok/s compared to Google: Gemini 3.1 Pro Preview Custom Tools's 117 tok/s, making it 2.9x faster for streaming responses. Time to first token is 0.31s for Google: Gemini 2.5 Flash vs 21.91s for Google: Gemini 3.1 Pro Preview Custom Tools, which affects perceived responsiveness in interactive applications.
Pricing
Google: Gemini 2.5 Flash is more affordable at $0.30/1M input tokens ($2.50/1M output), while Google: Gemini 3.1 Pro Preview Custom Tools costs $2.00/1M input ($12/1M output). That makes Google: Gemini 3.1 Pro Preview Custom Tools 6.7x more expensive per token, which can add up significantly at scale. For a typical workload of 100 requests per day at 2,000 tokens each, Google: Gemini 2.5 Flash would cost approximately $1.80/month vs $12.00/month for Google: Gemini 3.1 Pro Preview Custom Tools in input costs alone.
Context Window
Both models support the same context window of 1.0M tokens (approximately 524 pages of text). For output length, Google: Gemini 3.1 Pro Preview Custom Tools can generate up to 66K tokens per response vs 66K for Google: Gemini 2.5 Flash.
Best Use Cases
Choose Google: Gemini 2.5 Flash when you need faster output (343 tok/s), lower cost. Choose Google: Gemini 3.1 Pro Preview Custom Tools when you need higher intelligence (57.2), stronger coding performance (55.5).
Choose Google: Gemini 2.5 Flash if:
- ✓You need faster throughput (343 tok/s vs 117 tok/s)
- ✓You want lower latency (0.31s vs 21.91s TTFT)
- ✓Budget is a concern ($0.30/1M vs $2.00/1M)
Choose Google: Gemini 3.1 Pro Preview Custom Tools if:
- ✓You need higher intelligence (score: 57.2 vs 19.4)
- ✓You prioritize coding performance (score: 55.5 vs 14.5)
Frequently Asked Questions
Is Google: Gemini 2.5 Flash better than Google: Gemini 3.1 Pro Preview Custom Tools for coding?
Google: Gemini 3.1 Pro Preview Custom Tools scores higher on coding benchmarks (55.5 vs 14.5), making it the better choice for programming tasks.
Which is cheaper, Google: Gemini 2.5 Flash or Google: Gemini 3.1 Pro Preview Custom Tools?
Google: Gemini 2.5 Flash is cheaper at $0.30/1M input tokens vs $2.00/1M for Google: Gemini 3.1 Pro Preview Custom Tools.
Is Google: Gemini 2.5 Flash faster than Google: Gemini 3.1 Pro Preview Custom Tools?
Google: Gemini 2.5 Flash is faster, producing output at 343 tok/s compared to Google: Gemini 3.1 Pro Preview Custom Tools's 117 tok/s.
Can Google: Gemini 2.5 Flash process images?
Yes, Google: Gemini 2.5 Flash supports image input. Google: Gemini 3.1 Pro Preview Custom Tools also supports images.
Which has a larger context window, Google: Gemini 2.5 Flash or Google: Gemini 3.1 Pro Preview Custom Tools?
Both models have the same context window of 1.0M tokens.
Should I use Google: Gemini 2.5 Flash or Google: Gemini 3.1 Pro Preview Custom Tools?
It depends on your priorities. Google: Gemini 3.1 Pro Preview Custom Tools scores higher on intelligence (57.2), but Google: Gemini 2.5 Flash may be better for specific use cases like budget-conscious projects or speed-critical applications.
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Benchmark data by Artificial Analysis
Data last synced: March 24, 2026