Model Comparison
Grok-4 Fast Reasoning vs Phi 4 Reasoning PlusWhich is better in 2026?
Comparing Grok-4 Fast Reasoning and Phi 4 Reasoning Plus across benchmarks, pricing, and capabilities.
Verdict: Grok-4 Fast Reasoning vs Phi 4 Reasoning Plus — which is better?
Grok-4 Fast Reasoning (by xAI) and Phi 4 Reasoning Plus (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.
Choose Grok-4 Fast Reasoning if…
- you want the most recent training data — it shipped Aug 2025
Choose Phi 4 Reasoning Plus if…
- you need open weights you can self-host or fine-tune
Performance Benchmarks
Comparative analysis across standard metrics
Grok-4 Fast Reasoning and Phi 4 Reasoning Plusdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.
Arena Performance
Human preference votes
Context Window
Maximum input and output token capacity
Only Grok-4 Fast Reasoning specifies input context (2,000,000 tokens). Only Grok-4 Fast Reasoning specifies output context (30,000 tokens).
Input Capabilities
Supported data types and modalities
Grok-4 Fast Reasoning supports multimodal inputs, whereas Phi 4 Reasoning Plus does not.
Grok-4 Fast Reasoning can handle both text and other forms of data like images, making it suitable for multimodal applications.
Grok-4 Fast Reasoning
Phi 4 Reasoning Plus
License
Usage and distribution terms
Grok-4 Fast Reasoning is licensed under a proprietary license, while Phi 4 Reasoning Plus 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 Fast Reasoning was released on 2025-08-28, while Phi 4 Reasoning Plus was released on 2025-04-30.
Grok-4 Fast Reasoning is 4 months newer than Phi 4 Reasoning Plus.
Aug 28, 2025
11 months ago
4mo newerApr 30, 2025
1.3 years ago
Knowledge Cutoff
When training data ends
Phi 4 Reasoning Plus has a documented knowledge cutoff of 2025-03-01, while Grok-4 Fast Reasoning's cutoff date is not specified.
We can confirm Phi 4 Reasoning Plus's training data extends to 2025-03-01, but cannot make a direct comparison without Grok-4 Fast Reasoning's cutoff date.
—
Mar 2025
Outputs Comparison
Key Takeaways
Phi 4 Reasoning Plus
View detailsMicrosoft
Detailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against Grok-4 Fast Reasoning and Phi 4 Reasoning Plus side-by-side, then vote on the output you prefer.
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FAQ
Common questions about Grok-4 Fast Reasoning vs Phi 4 Reasoning Plus.