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Head-to-head comparison

Gemma 4 31B vs GPT-6 Luna

Gemma 4 31B (Google) and GPT-6 Luna (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 22 September 2026

As of 22 September 2026, GPT-6 Luna holds the stronger ModelCap Index position (#25 vs #29); Gemma 4 31B is 1.5× cheaper per output token ($0.34/1M vs $0.50/1M); GPT-6 Luna offers the longer context window (1M vs 262K tokens); and Gemma 4 31B ships open weights.

Which should you choose?

Choose Gemma 4 31B if…

  • API cost matters — $0.34/1M output tokens against $0.50/1M, about 1.5× cheaper.
  • your workload is prompt-heavy — input tokens cost $0.09/1M against $0.10/1M.
  • you want to self-host: Gemma 4 31B ships open weights while GPT-6 Luna is api only.
  • you want provider choice — 11 listed API providers against 2.

Choose GPT-6 Luna if…

  • you want the stronger overall ModelCap Index position — #25 against #29 (78.6 vs 73.8 points).
  • you need the longer context window — 1M tokens against 262K.
  • AA Humanity's Last Exam is your yardstick — 38.5% against 11.8%.
  • you want the more recently listed model — GPT-6 Luna was listed 22 September 2026, Gemma 4 31B 2 April 2026.

Gemma 4 31B vs GPT-6 Luna: specs, pricing and context

Specification comparison of Gemma 4 31B and GPT-6 Luna
FieldGemma 4 31BGoogleGPT-6 LunaOpenAI
ModelCap Index position#29#25
Index score73.878.6
EvidenceMeasuredMeasured
Input price / 1M tokens$0.09$0.10
Output price / 1M tokens$0.34$0.50
Context window262K tokens1M tokens
Max output tokens16K128K
API providers listed112
Weight accessOpen weightsAPI only
Input modalitiesImage, Text, VideoFile, Image, Text
First listed2 April 202622 September 2026
PublisherGoogleOpenAI

Evidence: 3 public benchmark observations across 3 boards · 3 public benchmark observations across 3 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Gemma 4 31B vs GPT-6 Luna

Public benchmark boards where Gemma 4 31B or GPT-6 Luna has a published result
BoardGemma 4 31BGPT-6 LunaLeads
Arena codingArena (LMArena)14991483–1514—Only one result
ARC-AGI-2ARC Prize Foundation—59.3%MaxOnly one result
ARC-AGI-3ARC Prize Foundation—0.2%MediumOnly one result
AA Intelligence IndexArtificial Analysis—37.3intelligence-index:v4.3:maxOnly one result
AA τ²-Bench TelecomArtificial Analysis65.5%tau2:telecom:dual-control:pass-at-1:3-repeats:source-model="Gemma 4 31B (Non-reasoning)":reasoning=false—Only one result
AA Humanity's Last ExamArtificial Analysis11.8%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="Gemma 4 31B (Non-reasoning)":reasoning=false38.5%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="GPT-6 Luna (max)":reasoning=trueGPT-6 Luna
WildClawBench OpenClawWildClawBench37.6—Only one result

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

Gemma 4 31B vs GPT-6 Luna: common questions

Is Gemma 4 31B better than GPT-6 Luna?

GPT-6 Luna ranks higher on the ModelCap Index as of 22 September 2026: #25 against #29. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it. Their published uncertainty intervals overlap, so the rank difference alone does not establish a reliable capability advantage for your workload.

Is Gemma 4 31B cheaper than GPT-6 Luna?

Gemma 4 31B is cheaper on output tokens: $0.34/1M against $0.50/1M. Input tokens are $0.09/1M for Gemma 4 31B and $0.10/1M for GPT-6 Luna. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $0.35 for Gemma 4 31B versus $0.45 for GPT-6 Luna. Gemma 4 31B costs 22.2% less in this scenario. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.

Which has the bigger context window, Gemma 4 31B or GPT-6 Luna?

GPT-6 Luna has the larger context window: 1M tokens against 262K.

Which is better for coding, Gemma 4 31B or GPT-6 Luna?

The two models do not share a coding benchmark board on ModelCap yet, so no head-to-head coding score is published; the ModelCap Index position is the closest overall signal.

Are Gemma 4 31B and GPT-6 Luna open-weight models?

Gemma 4 31B: Open weights. GPT-6 Luna: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run Gemma 4 31B and GPT-6 Luna?

ModelCap currently lists 11 API providers for Gemma 4 31B and 2 for GPT-6 Luna, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Gemma 4 31B vs GPT-6 Luna comparison?

Every figure comes from the sealed ModelCap dataset published 22 September 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.

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