OpenAI: GPT-6 Luna (batch) vs Google: Gemini 3.8 Flash
Side-by-side comparison of specs, pricing, benchmark scores, and task rankings. Updated 2026-09-27.
| OpenAI: GPT-6 Luna (batch) | Google: Gemini 3.8 Flash | |
|---|---|---|
| Vendor | openai | |
| Quality Score | 100 | 100 |
| Benchmark Score | 62.2 | 69.0 |
| Input Price | $0.05/M | $0.75/M |
| Output Price | $0.25/M | $3.75/M |
| Context Window | 1,050,000 | 1,048,576 |
| Max Output | 128,000 | 65,536 |
| Tool Calling | ✓ | ✓ |
| Structured Output | ✓ | ✓ |
| Reasoning Mode | ✓ | ✓ |
| Vision | ✓ | ✓ |
| Audio | - | ✓ |
| Benchmark Scores | ||
| ai_index | 61.5 | 67.5 |
The verdict
For a sample job of 1 million input tokens and 250,000 output tokens, GPT-6 Luna (batch) costs $0.11 and Gemini 3.8 Flash costs $1.69, so GPT-6 Luna (batch) is about 15.0 times cheaper for the same work.
Both take in a similar amount of text: 1,050,000 and 1,048,576 tokens, about 1,575 and 1,573 pages.
Only Gemini 3.8 Flash offers audio input and video input.
On our blended benchmark score Gemini 3.8 Flash leads 69.0 to 62.2.
Across the 20 tasks where they differ, GPT-6 Luna (batch) scores higher on 7 (Code Completion, Code Documentation, Regex Writing and others), Gemini 3.8 Flash on 13 (SQL Generation, Code Review, Code Refactoring and others).
Pick GPT-6 Luna (batch) if you need lower cost; pick Gemini 3.8 Flash if you need audio input, video input or benchmark performance.
Costs use current list prices per million tokens; page counts assume about 0.75 words per token and 500 words per page.
Who wins by task?
| Task | OpenAI: GPT-6 Luna (batch) | Google: Gemini 3.8 Flash |
|---|---|---|
| SQL Generation | 141 | 141 |
| Code Review | 143 | 144 |
| Code Completion | 133 | 132 |
| Code Refactoring | 145 | 146 |
| Bug Fixing | 147 | 148 |
| Unit Test Generation | 131 | 132 |
| Code Documentation | 137 | 137 |
| Regex Writing | 126 | 125 |
| CI/CD Pipelines | 127 | 128 |
| Frontend Component Design | 129 | 130 |
| Data Analysis | 133 | 134 |
| CSV / Spreadsheet Cleanup | 136 | 136 |
| ETL Scripting | 136 | 137 |
| JSON Extraction | 131 | 131 |
| Bulk Data Labeling | 129 | 128 |
| OCR / Document Parsing | 134 | 134 |
| Table Extraction from PDFs | 134 | 134 |
| Long-Document Summarization | 147 | 148 |
| Short-Form Summarization | 127 | 126 |
| Blog Post Writing | 129 | 129 |
Scores reflect capability match + benchmark data + pricing for each task. Methodology →