Model Comparison
Grok-4.1 Fast Reasoning vs Phi-4-multimodal-instructWhich is better in 2026?
Comparing Grok-4.1 Fast Reasoning and Phi-4-multimodal-instruct across benchmarks, pricing, and capabilities.
Verdict: Grok-4.1 Fast Reasoning vs Phi-4-multimodal-instruct — which is better?
Grok-4.1 Fast Reasoning (by xAI) and Phi-4-multimodal-instruct (by Microsoft) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.
On price, Phi-4-multimodal-instruct is roughly 4.4x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Grok-4.1 Fast Reasoning also accepts a larger context window (2,000,000 input tokens), making it the stronger choice for long documents and large codebases.
Choose Grok-4.1 Fast Reasoning if…
- you process long inputs — it offers a 2,000,000 token context window
- you want the most recent training data — it shipped Nov 2025
Choose Phi-4-multimodal-instruct if…
- cost matters — it's about 4.4x cheaper per token
- you need open weights you can self-host or fine-tune
Performance Benchmarks
Comparative analysis across standard metrics
Grok-4.1 Fast Reasoning and Phi-4-multimodal-instructdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.
Arena Performance
Human preference votes
Pricing Analysis
Price comparison per million tokens
For input processing, Grok-4.1 Fast Reasoning ($0.20/1M tokens) is 4.0x more expensive than Phi-4-multimodal-instruct ($0.05/1M tokens).
For output processing, Grok-4.1 Fast Reasoning ($0.50/1M tokens) is 5.0x more expensive than Phi-4-multimodal-instruct ($0.10/1M tokens).
In conclusion, Grok-4.1 Fast Reasoning is more expensive than Phi-4-multimodal-instruct.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Grok-4.1 Fast Reasoning accepts 2,000,000 input tokens compared to Phi-4-multimodal-instruct's 128,000 tokens. Phi-4-multimodal-instruct can generate longer responses up to 128,000 tokens, while Grok-4.1 Fast Reasoning is limited to 30,000 tokens.
Input Capabilities
Supported data types and modalities
Both Grok-4.1 Fast Reasoning and Phi-4-multimodal-instruct support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Grok-4.1 Fast Reasoning
Phi-4-multimodal-instruct
License
Usage and distribution terms
Grok-4.1 Fast Reasoning is licensed under a proprietary license, while Phi-4-multimodal-instruct uses MIT.
License differences may affect how you can use these models in commercial or open-source projects.
Proprietary
Closed source
MIT
Open weights
Release Timeline
When each model was launched
Grok-4.1 Fast Reasoning was released on 2025-11-17, while Phi-4-multimodal-instruct was released on 2025-02-01.
Grok-4.1 Fast Reasoning is 10 months newer than Phi-4-multimodal-instruct.
Nov 17, 2025
7 months ago
9mo newerFeb 1, 2025
1.4 years ago
Knowledge Cutoff
When training data ends
Phi-4-multimodal-instruct has a documented knowledge cutoff of 2024-06-01, while Grok-4.1 Fast Reasoning's cutoff date is not specified.
We can confirm Phi-4-multimodal-instruct's training data extends to 2024-06-01, but cannot make a direct comparison without Grok-4.1 Fast Reasoning's cutoff date.
—
Jun 2024
Provider Availability
Grok-4.1 Fast Reasoning is available from xAI. Phi-4-multimodal-instruct is available from DeepInfra.
Grok-4.1 Fast Reasoning
Phi-4-multimodal-instruct
Outputs Comparison
Key Takeaways
Detailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against Grok-4.1 Fast Reasoning and Phi-4-multimodal-instruct side-by-side, then vote on the output you prefer.
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FAQ
Common questions about Grok-4.1 Fast Reasoning vs Phi-4-multimodal-instruct.