Grok-4.1 Fast Reasoning vs Llama 3.1 70B Instruct
Comparing Grok-4.1 Fast Reasoning and Llama 3.1 70B Instruct across benchmarks, pricing, and capabilities.
xAI · Meta · Updated for 2026
Which is better?
Grok-4.1 Fast Reasoning and Llama 3.1 70B Instruct trade strengths across price, capabilities, and technical limits. The better choice depends on the workload.
On price, Llama 3.1 70B Instruct is roughly 1.4x 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.
Based on current benchmark, pricing, and model metadata for 2026.
Choose Grok-4.1 Fast Reasoning
- 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 Llama 3.1 70B Instruct
- cost matters — it's about 1.4x cheaper per token
- you need open weights you can self-host or fine-tune
At a glance
The differences that matter most.
Performance Benchmarks
Comparative analysis across standard metrics
Grok-4.1 Fast Reasoning and Llama 3.1 70B Instructdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.
Arena Performance
Playground indexes and blind preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Grok-4.1 Fast Reasoning ($0.20/1M tokens) costs the same as Llama 3.1 70B Instruct ($0.20/1M tokens).
For output processing, Grok-4.1 Fast Reasoning ($0.50/1M tokens) is 2.5x more expensive than Llama 3.1 70B Instruct ($0.20/1M tokens).
In conclusion, Grok-4.1 Fast Reasoning is more expensive than Llama 3.1 70B 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 Llama 3.1 70B Instruct's 128,000 tokens. Llama 3.1 70B 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
Grok-4.1 Fast Reasoning supports multimodal inputs, whereas Llama 3.1 70B Instruct does not.
Grok-4.1 Fast Reasoning can handle both text and other forms of data like images, making it suitable for multimodal applications.
Grok-4.1 Fast Reasoning
Llama 3.1 70B Instruct
License
Usage and distribution terms
Grok-4.1 Fast Reasoning is licensed under a proprietary license, while Llama 3.1 70B Instruct uses Llama 3.1 Community License.
License differences may affect how you can use these models in commercial or open-source projects.
Proprietary
Closed source
Llama 3.1 Community License
Open weights
Release Timeline
When each model was launched
Grok-4.1 Fast Reasoning was released on 2025-11-17, while Llama 3.1 70B Instruct was released on 2024-07-23.
Grok-4.1 Fast Reasoning is 16 months newer than Llama 3.1 70B Instruct.
Nov 17, 2025
9 months ago
1.3yr newerJul 23, 2024
2.1 years ago
Knowledge Cutoff
When training data ends
Neither model specifies a knowledge cutoff date.
Unable to compare the recency of their training data.
Provider Availability
Grok-4.1 Fast Reasoning is available from xAI. Llama 3.1 70B Instruct is available from Lambda, DeepInfra, Hyperbolic, Groq, Cerebras, Together, Fireworks, Bedrock, Sambanova.
Grok-4.1 Fast Reasoning
Llama 3.1 70B Instruct
Outputs Comparison
Judge for yourself.
Run your own prompts against Grok-4.1 Fast Reasoning and Llama 3.1 70B Instruct side-by-side, then vote on the output you prefer.
FAQ
Common questions about Grok-4.1 Fast Reasoning vs Llama 3.1 70B Instruct.