Model comparison
Gemini 3.1 Pro Preview vs Grok 4.20 Reasoning
Compare Gemini 3.1 Pro Preview vs Grok 4.20 Reasoning API pricing: input/output token costs, cache pricing, context windows, workload estimates, and routing fit.
Gemini 3.1 Pro Preview
gemini · gemini/gemini-3.1-pro-preview
- Input
- $2
- Output
- $12
- Context
- 1M
Grok 4.20 Reasoning
xai · grok-4.20-0309-reasoning
- Input
- $1.25
- Output
- $2.5
- Context
- 1M
Quick take
Grok 4.20 Reasoning has the lower input price at $1.25 per 1M input tokens. Grok 4.20 Reasoning is cheaper for the example blended workload below. Gemini 3.1 Pro Preview has the larger context window at 1M tokens.
Choose Gemini 3.1 Pro Preview if...
- Gemini 3.1 Pro Preview is safer for long documents, repository analysis, and RAG prompts because it has the larger context window.
- Gemini 3.1 Pro Preview is required if images, screenshots, or visual documents are part of the workflow.
Choose Grok 4.20 Reasoning if...
- Grok 4.20 Reasoning is the better default for cost-sensitive traffic and repeated high-volume calls.
- Grok 4.20 Reasoning gives more room for long generated answers, reports, or code output.
Example workload cost
Estimates use input tokens plus 20% output tokens. They exclude provider discounts, cache hits, and tool/search surcharges.
| Workload | Gemini 3.1 Pro Preview | Grok 4.20 Reasoning | Cheaper |
|---|---|---|---|
| 1M input + 200K output | $4.40 | $1.75 | Grok 4.20 Reasoning |
| 10M input + 2M output | $44.00 | $17.50 | Grok 4.20 Reasoning |
| 100M input + 20M output | $440.00 | $175.00 | Grok 4.20 Reasoning |
Context, output, and capability fit
Gemini 3.1 Pro Preview provides the larger context window. Check max output separately when the task needs long reports, code generation, or full-document rewrites.
- Gemini 3.1 Pro Preview max output
- 65.5K
- Grok 4.20 Reasoning max output
- 1M
- Gemini 3.1 Pro Preview features
- prompt caching, function calling, vision
- Grok 4.20 Reasoning features
- prompt caching, function calling
Risk notes for Gemini 3.1 Pro Preview
- Preview or beta model: verify availability and pricing before production rollout.
Risk notes for Grok 4.20 Reasoning
- No major capability risk is flagged in this snapshot, but provider pages should still be verified before production routing.
Routing tags
frontierpreviewreasoninglong-contextmultimodalenterprise-ragragagents