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AnthropicClaude Opus 5VSGoogleGemini 3.5 Flash

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

Our Take

We recommend Claude Opus 5 if your workflow requires peak coding capability, or the 3.0x cheaper Gemini 3.5 Flash to optimize your API budget. While both models deliver similar reasoning performance, Claude Opus 5 holds a clear lead in coding. Choose Claude Opus 5 for complex development tasks, or Gemini 3.5 Flash for cost optimization.
▶WHY?
Benchmark Calculations & Evidence:
  • Coding Benchmarks: Both models were evaluated on the SWE-bench Pro benchmark. Claude Opus 5 scored 79.2%, while Gemini 3.5 Flash scored 55.1%.
  • Reasoning Benchmarks: Both models were evaluated on the GPQA Diamond benchmark. Claude Opus 5 scored 93.7%, while Gemini 3.5 Flash scored 92.2%.
  • Cost Efficiency: Gemini 3.5 Flash pricing ($1.5/M input, $9/M output) is 3.0x cheaper than Claude Opus 5 ($5/M input, $25/M output).
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    Model Specs

    Claude Opus 5

    Website

    Benchmarks & Scores

    Coding (swe-bench-pro)Winner (+24.1%)
    79.2%

    complex codebases, multi-file repositories, and architectural planning

    Reasoning (gpqa-diamond)Winner (+1.5%)
    93.7%

    graduate-level science QA

    Cost & Context

    Cost (per 1M tokens)
    $10.00Input: $5.00 | Output: $25.00
    Context Window
    1.05M tokens
    Model Specs

    Gemini 3.5 Flash

    Website

    Benchmarks & Scores

    Coding (swe-bench-pro)
    55.1%

    complex codebases, multi-file repositories, and architectural planning

    Reasoning (gpqa-diamond)
    92.2%

    graduate-level science QA

    Cost & Context

    Cost (per 1M tokens)3.0x cheaper
    $3.38Input: $1.50 | Output: $9.00
    Context Window
    1.05M tokens
    Read our data collection methodology

    Frequently Asked Questions about Claude Opus 5 vs Gemini 3.5 Flash

    Gemini 3.5 Flash is cheaper than Claude Opus 5. Gemini 3.5 Flash has a blended cost of $3.38/1M tokens, which is about 3.0x cheaper than Claude Opus 5 at $10.00/1M tokens.

    Claude Opus 5 is better for coding tasks on this benchmark. It scores 79.2% on swe-bench-pro (complex codebases, multi-file repositories, and architectural planning) compared to Gemini 3.5 Flash which scores 55.1%.

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