GoogleGemini 3.5 FlashVSOpenAIGPT-5.6 Luna

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

Our Take

GPT-5.6 Luna is the clear winner here. It beats Gemini 3.5 Flash across the board because it is both smarter and cheaper to run. Unless you have specific platform restrictions, go with GPT-5.6 Luna—it is the optimal choice.

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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)

$3.38Input: $1.50 | Output: $9.00

Context Window

1.05M tokens

Model Specs

GPT-5.6 Luna

Website

Benchmarks & Scores

Coding (swe-bench-pro)Winner (+7.6%)

62.7%

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

Reasoning (gpqa-diamond)Winner (+0.1%)

92.3%

graduate-level science QA

Cost & Context

Cost (per 1M tokens)1.5x cheaper

$2.25Input: $1.00 | Output: $6.00

Context WindowLarger

1.05M tokens

Read our data collection methodology

Frequently Asked Questions about Gemini 3.5 Flash vs GPT-5.6 Luna

GPT-5.6 Luna is cheaper than Gemini 3.5 Flash. GPT-5.6 Luna has a blended cost of $2.25/1M tokens, which is about 1.5x cheaper than Gemini 3.5 Flash at $3.38/1M tokens.

GPT-5.6 Luna is better for coding tasks on this benchmark. It scores 62.7% 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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