Gemini 3.1 Flash-Lite vs Phi-4 Reasoning Vision 15B
Gemini 3.1 Flash-Lite (2026) and Phi-4 Reasoning Vision 15B (2026) are general-purpose language models from Google DeepMind and Microsoft Research. Gemini 3.1 Flash-Lite ships a 1M-token context window, while Phi-4 Reasoning Vision 15B ships a not-yet-sourced context window. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Gemini 3.1 Flash-Lite is safer overall; choose Phi-4 Reasoning Vision 15B when vision-heavy evaluation matters.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Flash-Lite | Phi-4 Reasoning Vision 15B |
|---|---|---|
| Best for | multimodal apps, tool-calling agents, and long-context analysis | multimodal apps |
| Decision fit | Coding, RAG, and Agents | Vision |
| Context window | 1M | — |
| Cheapest output | $1.50/1M tokens | - |
| Provider routes | 3 tracked | 0 tracked |
| Shared benchmarks | 0 shared | 0 shared |
Decision tradeoffs
- Gemini 3.1 Flash-Lite has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Gemini 3.1 Flash-Lite has broader tracked provider coverage for fallback and route flexibility.
- Gemini 3.1 Flash-Lite uniquely exposes JSON / Tool use, Structured outputs, and Code execution in local model data.
- Local decision data tags Gemini 3.1 Flash-Lite for Coding, RAG, and Agents.
- Local decision data tags Phi-4 Reasoning Vision 15B for Vision.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Gemini 3.1 Flash-Lite
$575
Cheapest tracked route/tier: Google AI Studio
Phi-4 Reasoning Vision 15B
Unavailable
No complete token price in local provider data
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-Lite and Phi-4 Reasoning Vision 15B; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for JSON / Tool use, Structured outputs, and Code execution before moving production traffic.
- No overlapping tracked provider route is sourced for Phi-4 Reasoning Vision 15B and Gemini 3.1 Flash-Lite; plan for SDK, billing, or endpoint changes.
- Gemini 3.1 Flash-Lite adds JSON / Tool use, Structured outputs, and Code execution in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-05-07 | 2026-03-12 |
| Context window | 1M | — |
| Parameters | — | 15B |
| Architecture | Decoder Only | - |
| License | Proprietary | MITOSI-approved |
| Openness | Proprietary | Open source |
| Weights | Not released | Unknown |
| Code | Unknown | Unknown |
| Commercial use | Restricted | Permitted |
| Knowledge cutoff | 2025-01 | 2025-03 |
Pricing and availability
| Pricing attribute | Gemini 3.1 Flash-Lite | Phi-4 Reasoning Vision 15B |
|---|---|---|
| Input price | $0.25/1M tokens | - |
| Output price | $1.50/1M tokens | - |
| Providers | - |
Capabilities
| Capability | Gemini 3.1 Flash-Lite | Phi-4 Reasoning Vision 15B |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | No | No |
| JSON / Tool use | Yes | No |
| Structured outputs | Yes | No |
| Code execution | Yes | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark scores are currently available for this pair.
Deep dive
The capability footprint differs most on JSON / Tool use: Gemini 3.1 Flash-Lite, JSON / Tool use: Gemini 3.1 Flash-Lite, structured outputs: Gemini 3.1 Flash-Lite, and code execution: Gemini 3.1 Flash-Lite. Both models share vision and multimodal input, 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-Lite has $0.25/1M input tokens and Phi-4 Reasoning Vision 15B has no token price listed. Provider availability is 3 listed routes versus 0. Treat unknown pricing as an integration gap, then verify the route you will actually call before estimating production spend.
Choose Gemini 3.1 Flash-Lite when coding workflow support and broader provider choice are central to the workload. Choose Phi-4 Reasoning Vision 15B when vision-heavy evaluation 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
Is Gemini 3.1 Flash-Lite or Phi-4 Reasoning Vision 15B open source?
Gemini 3.1 Flash-Lite is listed under Proprietary. Phi-4 Reasoning Vision 15B is listed under MIT. 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 vision, Gemini 3.1 Flash-Lite or Phi-4 Reasoning Vision 15B?
Both Gemini 3.1 Flash-Lite and Phi-4 Reasoning Vision 15B expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for multimodal input, Gemini 3.1 Flash-Lite or Phi-4 Reasoning Vision 15B?
Both Gemini 3.1 Flash-Lite and Phi-4 Reasoning Vision 15B expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for JSON / Tool use, Gemini 3.1 Flash-Lite or Phi-4 Reasoning Vision 15B?
Gemini 3.1 Flash-Lite has the clearer documented JSON / Tool use signal in this comparison. If JSON / Tool use is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for JSON / Tool use, Gemini 3.1 Flash-Lite or Phi-4 Reasoning Vision 15B?
Gemini 3.1 Flash-Lite has the clearer documented JSON / Tool use signal in this comparison. If JSON / 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-Lite and Phi-4 Reasoning Vision 15B?
Gemini 3.1 Flash-Lite is available on Google AI Studio, OpenRouter, and Vercel AI Gateway. Provider coverage can affect latency, region availability, compliance posture, and fallback options. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
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Last reviewed: 2026-10-17. Data sourced from public model cards and provider documentation.