Gemini 3.1 Flash TTS Preview vs Grok 4.20
Gemini 3.1 Flash TTS Preview (2026) and Grok 4.20 (2026) are frontier reasoning models from Google DeepMind and xAI. Gemini 3.1 Flash TTS Preview ships a 16K-token context window, while Grok 4.20 ships a 2M-token context window. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing.
Grok 4.20 fits 125x more tokens; pick it for long-context work and Gemini 3.1 Flash TTS Preview for tighter calls.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Flash TTS Preview | Grok 4.20 |
|---|---|---|
| Decision fit | General | Coding, RAG, and Agents |
| Context window | 16K | 2M |
| Cheapest output | - | $2.5/1M tokens |
| Provider routes | 0 tracked | 2 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Use Gemini 3.1 Flash TTS Preview when your own prompt tests beat the comparison signals; the local data does not show a decisive standalone advantage yet.
- Grok 4.20 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Grok 4.20 has broader tracked provider coverage for fallback and procurement flexibility.
- Grok 4.20 uniquely exposes Reasoning, Function calling, and Tool use in local model data.
- Local decision data tags Grok 4.20 for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
Gemini 3.1 Flash TTS Preview
Unavailable
No complete token price in local provider data
Grok 4.20
$1,625
Cheapest tracked route: xAI Console
Cost delta unavailable until both models have sourced input and output token prices.
Switch friction
- No overlapping tracked provider route is sourced for Gemini 3.1 Flash TTS Preview and Grok 4.20; plan for SDK, billing, or endpoint changes.
- Grok 4.20 adds Reasoning, Function calling, and Tool use in local capability data.
- No overlapping tracked provider route is sourced for Grok 4.20 and Gemini 3.1 Flash TTS Preview; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for Reasoning, Function calling, and Tool use before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-15 | 2026-01-01 |
| Context window | 16K | 2M |
| Parameters | — | — |
| Architecture | decoder only | - |
| License | Proprietary | Proprietary |
| Knowledge cutoff | - | - |
Pricing and availability
| Pricing attribute | Gemini 3.1 Flash TTS Preview | Grok 4.20 |
|---|---|---|
| Input price | - | $1.25/1M tokens |
| Output price | - | $2.5/1M tokens |
| Providers | - |
Capabilities
| Capability | Gemini 3.1 Flash TTS Preview | Grok 4.20 |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | No | Yes |
| Function calling | No | Yes |
| Tool use | No | Yes |
| Structured outputs | No | Yes |
| Code execution | No | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on reasoning mode: Grok 4.20, function calling: Grok 4.20, tool use: Grok 4.20, and structured outputs: Grok 4.20. Both models share the core language-model surface, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
Pricing coverage is uneven: Gemini 3.1 Flash TTS Preview has no token price sourced yet and Grok 4.20 has $1.25/1M input tokens. Provider availability is 0 tracked routes versus 2. Treat unknown pricing as an integration gap, then verify the route you will actually call before estimating production spend.
Choose Gemini 3.1 Flash TTS Preview when provider fit are central to the workload. Choose Grok 4.20 when reasoning depth, larger context windows, and broader provider choice are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions. It also helps separate model capability from provider packaging, which can change cost and latency.
FAQ
Which has a larger context window, Gemini 3.1 Flash TTS Preview or Grok 4.20?
Grok 4.20 supports 2M tokens, while Gemini 3.1 Flash TTS Preview supports 16K tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Is Gemini 3.1 Flash TTS Preview or Grok 4.20 open source?
Gemini 3.1 Flash TTS Preview is listed under Proprietary. Grok 4.20 is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for reasoning mode, Gemini 3.1 Flash TTS Preview or Grok 4.20?
Grok 4.20 has the clearer documented reasoning mode signal in this comparison. If reasoning mode is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for function calling, Gemini 3.1 Flash TTS Preview or Grok 4.20?
Grok 4.20 has the clearer documented function calling signal in this comparison. If function calling is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for tool use, Gemini 3.1 Flash TTS Preview or Grok 4.20?
Grok 4.20 has the clearer documented tool use signal in this comparison. If tool use is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Gemini 3.1 Flash TTS Preview and Grok 4.20?
Gemini 3.1 Flash TTS Preview is available on the tracked providers still being sourced. Grok 4.20 is available on xAI Console and OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-14. Data sourced from public model cards and provider documentation.