GoogleGemini 3.5 FlashVSOpenAIGPT-5.5

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

Our Take

Both models perform almost identically, with an average score gap of just 2.4%. We recommend choosing Gemini 3.5 Flash as it is the more cost-effective option (being 3.3x cheaper) without sacrificing any real-world capability.

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Model Specs

Gemini 3.5 Flash

Website

Benchmarks & Scores

Coding (swe-bench-pro)

55.1%

excellent at multi-file repositories, autonomous agents, and industrial codebases

Reasoning (gpqa-diamond)

92.2%

graduate-level science QA

Cost & Context

Cost (per 1M tokens)3.3x cheaper

$3.38Input: $1.50 | Output: $9.00

Context Window

1.05M tokens

Model Specs

GPT-5.5

Website

Benchmarks & Scores

Coding (swe-bench-pro)Winner (+3.5%)

58.6%

excellent at multi-file repositories, autonomous agents, and industrial codebases

Reasoning (gpqa-diamond)Winner (+1.4%)

93.6%

graduate-level science QA

Cost & Context

Cost (per 1M tokens)

$11.25Input: $5.00 | Output: $30.00

Context WindowLarger

1.05M tokens

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Frequently Asked Questions about Gemini 3.5 Flash vs GPT-5.5

Gemini 3.5 Flash is cheaper than GPT-5.5. Gemini 3.5 Flash has a blended cost of $3.38/1M tokens, which is about 3.3x cheaper than GPT-5.5 at $11.25/1M tokens.

GPT-5.5 is better for coding tasks on this benchmark. It scores 58.6% on swe-bench-pro (excellent at multi-file repositories, autonomous agents, and industrial codebases) compared to Gemini 3.5 Flash which scores 55.1%.

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