Gemini 3.1 Pro Preview vs Gemini 3.5 Flash
A side-by-side comparison of two multimodal models — real specs, pricing, strengths and weaknesses, and a clear verdict on which to choose. Kept current by our agents.
Quick verdict: which should you choose?
Choose Gemini 3.1 Pro Preview if you need
- ✓Higher intelligence (46.5 index) for complex multimodal reasoning
- ✓Effective large-scale document analysis with strong modality integration
- ✓Maximum 1M context utilization on demanding tasks
- ✓Native audio/image/video/text handling without added complexity
Choose Gemini 3.5 Flash if you need
- ✓Faster output speed (179.91 t/s) for high-volume workloads
- ✓Lower cost at $9 per 1M tokens versus $12
- ✓Efficient multimodal tasks where speed matters more than peak depth
- ✓Versatile data-type handling with reduced resource demands
Verdict
Gemini 3.1 Pro Preview leads with a higher intelligence index (46.5 vs 45.4) and stronger emphasis on complex multimodal integration and large-scale document analysis, while Gemini 3.5 Flash wins on speed (179.91 t/s vs 128.71 t/s) and lower price ($9 vs $12 per 1M tokens). Both share identical 1M context windows and native multimodal support for text, image, video, and audio. The Pro Preview suits depth-focused work despite preview inconsistencies, whereas Flash prioritizes efficiency at the cost of some task depth.
Gemini 3.1 Pro Preview vs Gemini 3.5 Flash: side by side
| Spec | Gemini 3.1 Pro Preview | Gemini 3.5 Flash | Winner |
|---|---|---|---|
| Intelligence | 46.5 | 45.4 | Gemini 3.1 Pro Preview |
| Output speed | 129 t/s | 180 t/s | Gemini 3.5 Flash |
| Output price | $12.00/1M | $9.00/1M | Gemini 3.5 Flash |
| Context | 1049K | 1049K | Tie |
| Params | — | — | Tie |
| Provider | Tie |
Detailed analysis
Intelligence
Winner: Gemini 3.1 Pro PreviewGemini 3.1 Pro Preview scores 46.5 on the intelligence index compared to 45.4 for Gemini 3.5 Flash. This edge aligns with its listed strengths in complex multimodal tasks and large-scale document analysis. The Flash model trades some depth for speed on specialized work.
Speed
Winner: Gemini 3.5 FlashGemini 3.5 Flash delivers 179.91 tokens per second versus 128.71 for Gemini 3.1 Pro Preview. Its strengths explicitly highlight high speed and efficiency. The Pro Preview notes higher resource use at maximum context, consistent with slower throughput.
Pricing
Winner: Gemini 3.5 FlashGemini 3.5 Flash costs $9 per million tokens while Gemini 3.1 Pro Preview costs $12. Both are proprietary Google models with identical context sizes. The price difference favors Flash for cost-sensitive, high-volume use.
Context & Multimodal
Winner: TieBoth models support a 1,048,576-token context and native audio, image, video, and text inputs. Pro Preview emphasizes strong integration and document analysis; Flash stresses versatility across data types. Limitations for each note context utilization depends on the specific task.
Gemini 3.1 Pro Preview
Pros
- +Handles up to 1M token contexts
- +Native support for audio, image, video, and text
- +Strong integration of multiple modalities
Cons
- –Preview model may show inconsistent outputs
- –High resource use with maximum context
- –Requires verification on complex tasks
Gemini 3.5 Flash
Pros
- +High speed and efficiency
- +Strong multimodal integration
- +Large context window support
Cons
- –Trades depth for speed on complex tasks
- –Variable performance on specialized domains
- –Context utilization depends on task
Summary: Gemini 3.1 Pro Preview vs Gemini 3.5 Flash
Choose Gemini 3.1 Pro Preview when intelligence and complex multimodal depth are priorities. Select Gemini 3.5 Flash for faster, cheaper operation on efficiency-focused workloads. Both deliver equivalent context and modality coverage from the same provider.
Frequently asked questions
Gemini 3.1 Pro Preview is better for complex tasks due to its higher intelligence index; Gemini 3.5 Flash is better when speed and cost are primary needs.