GoogleGemini 2.5 ProVSGoogleGemini 3.5 Flash

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

Our Take

We recommend Gemini 3.5 Flash for superior overall value and reasoning capabilities, as it is cheaper or equal in cost while delivering peak intelligence. While Gemini 3.5 Flash excels at complex complex codebases, multi-file repositories, and architectural planning, Gemini 2.5 Pro is suited for scripting multi-file code and clearly defined tasks. Choose Gemini 3.5 Flash for architectural codebase planning, or Gemini 2.5 Pro if you specifically require its simpler functions profile.

▶WHY?

Benchmark Calculations & Evidence:

Coding Evaluation: Gemini 2.5 Pro was evaluated on SWE-bench Verified (scoring 59.6%), while Gemini 3.5 Flash was evaluated on SWE-bench Pro (scoring 55.1%).

Reasoning Accuracy: Both models were evaluated on the GPQA Diamond benchmark. Gemini 3.5 Flash scored 92.2%, while Gemini 2.5 Pro scored 84.4%.

Cost Efficiency: Gemini 2.5 Pro pricing ($1.25/M input, $10/M output) is 1.0x cheaper than Gemini 3.5 Flash ($1.5/M input, $9/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)

$3.44Input: $1.25 | Output: $10.00

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)Winner (+7.8%)

92.2%

graduate-level science QA

Cost & Context

Cost (per 1M tokens)

$3.38Input: $1.50 | Output: $9.00

Context Window

1.05M tokens

Read our data collection methodology

Frequently Asked Questions about Gemini 2.5 Pro vs Gemini 3.5 Flash

Gemini 3.5 Flash is cheaper than Gemini 2.5 Pro. Gemini 3.5 Flash has a blended cost of $3.38/1M tokens, which is about 1.0x cheaper than Gemini 2.5 Pro at $3.44/1M tokens.

For coding tasks, Gemini 2.5 Pro scores 59.6% on swe-bench-verified (multi-file code and clearly defined tasks), while Gemini 3.5 Flash scores 55.1% on swe-bench-pro (complex codebases, multi-file repositories, and architectural planning).

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