Gemini 3.5 Flash vs GPT-5.6 Luna
Gemini 3.5 Flash and GPT-5.6 Luna are closely matched at 43.0 and 45.4 on the LLM Stats Score. GPT-5.6 Luna is 7.5x cheaper per token.
Google · OpenAI · Updated for 2026
Which is better?
Gemini 3.5 Flash and GPT-5.6 Luna are closely matched on the overall LLM Stats Score at 43.0 and 45.4.
In the 5 individual benchmarks reported for both models, GPT-5.6 Luna wins 3; this is a narrower head-to-head signal than the composite indexes.
On price, GPT-5.6 Luna is roughly 7.5x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-5.6 Luna also accepts a larger context window (1,050,000 input tokens), making it the stronger choice for long documents and large codebases.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose Gemini 3.5 Flash
- you want predictable pricing at $1.50/M input and $9.00/M output
Choose GPT-5.6 Luna
- you value its reported benchmark strengths — it wins 3 of 5 exact shared results
- cost matters — it's about 7.5x cheaper per token
- you process long inputs — it offers a 1,050,000 token context window
- you want the most recent training data — it shipped Jul 2026
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
1 more shared indexes
Individual benchmarks
16 reported for Gemini 3.5 Flash · 45 for GPT-5.6 Luna
Gemini 3.5 Flash outperforms in 2 benchmarks (MMMU-Pro, Toolathlon), while GPT-5.6 Luna is better at 3 benchmarks (DeepSWE 1.1, MRCR v2 (8-needle), SWE-Bench Pro).
GPT-5.6 Luna has a slight edge in benchmark performance.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Gemini 3.5 Flash ($1.50/1M tokens) is 7.5x more expensive than GPT-5.6 Luna ($0.20/1M tokens).
For output processing, Gemini 3.5 Flash ($9.00/1M tokens) is 7.5x more expensive than GPT-5.6 Luna ($1.20/1M tokens).
In conclusion, Gemini 3.5 Flash is more expensive than GPT-5.6 Luna.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-5.6 Luna accepts 1,050,000 input tokens compared to Gemini 3.5 Flash's 1,048,576 tokens. GPT-5.6 Luna can generate longer responses up to 128,000 tokens, while Gemini 3.5 Flash is limited to 65,536 tokens.
Input capabilities
Documented input modalities across available providers
Both Gemini 3.5 Flash and GPT-5.6 Luna support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Gemini 3.5 Flash
GPT-5.6 Luna
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Gemini 3.5 Flash was released on 2026-05-19, while GPT-5.6 Luna was released on 2026-07-09.
GPT-5.6 Luna is 2 months newer than Gemini 3.5 Flash.
May 19, 2026
3 months ago
Jul 9, 2026
1 months ago
1mo newerKnowledge Cutoff
When training data ends
Gemini 3.5 Flash has a knowledge cutoff of 2026-01-31, while GPT-5.6 Luna has a cutoff of 2026-02-16.
GPT-5.6 Luna has more recent training data (up to 2026-02-16), making it potentially better informed about events through that date compared to Gemini 3.5 Flash (2026-01-31).
Jan 2026
Feb 2026
1 mo newerProvider Availability
Gemini 3.5 Flash is available from Google. GPT-5.6 Luna is available from OpenAI.
Gemini 3.5 Flash
GPT-5.6 Luna
Outputs Comparison
Judge for yourself.
Run your own prompts against Gemini 3.5 Flash and GPT-5.6 Luna side-by-side, then vote on the output you prefer.
FAQ
Common questions about Gemini 3.5 Flash vs GPT-5.6 Luna.