GoogleGemini 2.5 ProVSGoogleGemini 3.1 Pro

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

Our Take

We recommend Gemini 3.1 Pro for complex complex codebases, multi-file repositories, and architectural planning, or the 1.3x cheaper Gemini 2.5 Pro if your budget requires optimizing costs for very high-volume pipelines. While Gemini 3.1 Pro offers a clear reasoning advantage, it carries a moderate price premium. Choose Gemini 3.1 Pro for architectural codebase planning, or Gemini 2.5 Pro to save on API costs for simple scripts.

▶WHY?

Benchmark Calculations & Evidence:

Coding Evaluation: Gemini 2.5 Pro was evaluated on SWE-bench Verified (scoring 59.6%), 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 Pro scored 84.4%.

Cost Efficiency: Gemini 2.5 Pro pricing ($1.25/M input, $10/M output) is 1.3x cheaper than Gemini 3.1 Pro ($2/M input, $12/M output).

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Model Specs

Gemini 2.5 Pro

Website

Benchmarks & Scores

Coding (swe-bench-verified)

59.6%

multi-file code and clearly defined tasks

Reasoning (gpqa-diamond)

84.4%

graduate-level science QA

Cost & Context

Cost (per 1M tokens)1.3x cheaper

$3.44Input: $1.25 | Output: $10.00

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 (+9.9%)

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 Pro vs Gemini 3.1 Pro

Gemini 2.5 Pro is cheaper than Gemini 3.1 Pro. Gemini 2.5 Pro has a blended cost of $3.44/1M tokens, which is about 1.3x cheaper than Gemini 3.1 Pro at $4.50/1M tokens.

For coding tasks, Gemini 2.5 Pro scores 59.6% 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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