GPT-5.1 vs Grok 4 Fast
Detailed comparison between GPT-5.1 and Grok 4 Fast for RAG applications. See which LLM best meets your accuracy, performance, and cost needs. If you want to compare these models on your data, try Agentset.
Model Comparison
GPT-5.1 takes the lead.
Both GPT-5.1 and Grok 4 Fast are powerful language models designed for RAG applications. However, their performance characteristics differ in important ways.
Why GPT-5.1:
- GPT-5.1 has 196 higher ELO rating
- GPT-5.1 has a 20.6% higher win rate
Overview
Key metrics
ELO Rating
Overall ranking quality
GPT-5.1
Grok 4 Fast
Win Rate
Head-to-head performance
GPT-5.1
Grok 4 Fast
Quality Score
Overall quality metric
GPT-5.1
Grok 4 Fast
Average Latency
Response time
GPT-5.1
Grok 4 Fast
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Visual Performance Analysis
Performance
ELO Rating Comparison
Win/Loss/Tie Breakdown
Quality Across Datasets (Overall Score)
Latency Distribution (ms)
Breakdown
How the models stack up
| Metric | GPT-5.1 | Grok 4 Fast | Description |
|---|---|---|---|
| Overall Performance | |||
| ELO Rating | 1689 | 1492 | Overall ranking quality based on pairwise comparisons |
| Win Rate | 65.5% | 44.9% | Percentage of comparisons won against other models |
| Quality Score | 4.97 | 4.96 | Average quality across all RAG metrics |
| Pricing & Context | |||
| Input Price per 1M | $1.25 | $0.20 | Cost per million input tokens |
| Output Price per 1M | $10.00 | $0.50 | Cost per million output tokens |
| Context Window | 400K | 2000K | Maximum context window size |
| Release Date | 2025-11-13 | 2025-09-19 | Model release date |
| Performance Metrics | |||
| Avg Latency | 16.2s | 5.9s | Average response time across all datasets |
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Agentset gives you a complete RAG API with top-ranked LLMs and smart retrieval built in. Upload your data, call the API, and get grounded answers from day one.
import { Agentset } from "agentset";
const agentset = new Agentset();
const ns = agentset.namespace("ns_1234");
const results = await ns.search(
"What is multi-head attention?"
);
for (const result of results) {
console.log(result.text);
}Dataset Performance
By benchmark
Comprehensive comparison of RAG quality metrics (correctness, faithfulness, grounding, relevance, completeness) and latency for each benchmark dataset.
MSMARCO
| Metric | GPT-5.1 | Grok 4 Fast | Description |
|---|---|---|---|
| Quality Metrics | |||
| Correctness | 4.97 | 4.90 | Factual accuracy of responses |
| Faithfulness | 4.97 | 4.90 | Adherence to source material |
| Grounding | 4.97 | 4.90 | Citations and context usage |
| Relevance | 5.00 | 5.00 | Query alignment and focus |
| Completeness | 4.93 | 4.83 | Coverage of all aspects |
| Overall | 4.97 | 4.91 | Average across all metrics |
| Latency Metrics | |||
| Mean | 9111ms | 3894ms | Average response time |
| Min | 3841ms | 1742ms | Fastest response time |
| Max | 34731ms | 6649ms | Slowest response time |
PG
| Metric | GPT-5.1 | Grok 4 Fast | Description |
|---|---|---|---|
| Quality Metrics | |||
| Correctness | 5.00 | 5.00 | Factual accuracy of responses |
| Faithfulness | 5.00 | 5.00 | Adherence to source material |
| Grounding | 5.00 | 5.00 | Citations and context usage |
| Relevance | 5.00 | 5.00 | Query alignment and focus |
| Completeness | 4.77 | 4.97 | Coverage of all aspects |
| Overall | 4.95 | 4.99 | Average across all metrics |
| Latency Metrics | |||
| Mean | 29008ms | 9142ms | Average response time |
| Min | 4393ms | 4767ms | Fastest response time |
| Max | 43887ms | 17055ms | Slowest response time |
SciFact
| Metric | GPT-5.1 | Grok 4 Fast | Description |
|---|---|---|---|
| Quality Metrics | |||
| Correctness | 5.00 | 5.00 | Factual accuracy of responses |
| Faithfulness | 5.00 | 5.00 | Adherence to source material |
| Grounding | 5.00 | 5.00 | Citations and context usage |
| Relevance | 4.97 | 4.97 | Query alignment and focus |
| Completeness | 4.97 | 4.90 | Coverage of all aspects |
| Overall | 4.99 | 4.97 | Average across all metrics |
| Latency Metrics | |||
| Mean | 10454ms | 4516ms | Average response time |
| Min | 4700ms | 2358ms | Fastest response time |
| Max | 21205ms | 14942ms | Slowest response time |
Explore More
Compare more LLMs
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