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GoogleGemini 2.5 FlashVSGoogleGemini 3.1 Pro

Analysis by:the whichllmmodel Editorial Team|Updated: June 2026

Our Take

We recommend Gemini 3.1 Pro if you need peak intelligence for complex complex codebases, multi-file repositories, and architectural planning, or the 5.3x cheaper Gemini 2.5 Flash if your workflow is limited to multi-file code and clearly defined tasks. While Gemini 3.1 Pro holds a major reasoning advantage, Gemini 2.5 Flash is optimized for high-volume budget pipelines. Choose Gemini 3.1 Pro for architectural codebase planning, or Gemini 2.5 Flash to maximize your budget for basic scripts.
▶WHY?
Benchmark Calculations & Evidence:
  • Coding Evaluation: Gemini 2.5 Flash was evaluated on SWE-bench Verified (scoring 60.4%), while Gemini 3.1 Pro was evaluated on SWE-bench Pro (scoring 54.2%).
  • Reasoning Accuracy: Both models were evaluated on the GPQA Diamond benchmark. Gemini 3.1 Pro scored 94.3%, while Gemini 2.5 Flash scored 68.3%.
  • Cost Efficiency: Gemini 2.5 Flash pricing ($0.3/M input, $2.5/M output) is 5.3x cheaper than Gemini 3.1 Pro ($2/M input, $12/M output).
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    Model Specs

    Gemini 2.5 Flash

    Website

    Benchmarks & Scores

    Coding (swe-bench-verified)
    60.4%

    multi-file code and clearly defined tasks

    Reasoning (gpqa-diamond)
    68.3%

    graduate-level science QA

    Cost & Context

    Cost (per 1M tokens)5.3x cheaper
    $0.85Input: $0.30 | Output: $2.50
    Context Window
    1.05M tokens
    Model Specs

    Gemini 3.1 Pro

    Website

    Benchmarks & Scores

    Coding (swe-bench-pro)
    54.2%

    complex codebases, multi-file repositories, and architectural planning

    Reasoning (gpqa-diamond)Winner (+26.0%)
    94.3%

    graduate-level science QA

    Cost & Context

    Cost (per 1M tokens)
    $4.50Input: $2.00 | Output: $12.00
    Context Window
    1.05M tokens
    Read our data collection methodology

    Frequently Asked Questions about Gemini 2.5 Flash vs Gemini 3.1 Pro

    Gemini 2.5 Flash is cheaper than Gemini 3.1 Pro. Gemini 2.5 Flash has a blended cost of $0.85/1M tokens, which is about 5.3x cheaper than Gemini 3.1 Pro at $4.50/1M tokens.

    For coding tasks, Gemini 2.5 Flash scores 60.4% on swe-bench-verified (multi-file code and clearly defined tasks), while Gemini 3.1 Pro scores 54.2% on swe-bench-pro (complex codebases, multi-file repositories, and architectural planning).

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