Grok 4.1 Fast vs Claude Opus 4

Compare Grok 4.1 Fast by xAI against Claude Opus 4 by Anthropic, in 1 community votes, claude opus 4 wins 100% of head-to-head duels, tested across 35 shared challenges. Updated April 2026.

Which is better, Grok 4.1 Fast or Claude Opus 4?

Claude Opus 4 is the better choice overall, winning 100% of 1 blind community votes on Rival. Compare their real outputs side by side below.

Key Differences Between Grok 4.1 Fast and Claude Opus 4

Grok 4.1 Fast is made by xai while Claude Opus 4 is from anthropic. In community voting, In 1 community votes, Claude Opus 4 wins 100% of head-to-head duels.

In 1 community votes, Claude Opus 4 wins 100% of head-to-head duels. Based on blind community voting from the Rival open dataset of 1+ human preference judgments for this pair.

Our Verdict
Claude Opus 4
Claude Opus 4Winner
Grok 4.1 Fast
Grok 4.1 FastRunner-up

Pick Claude Opus 4. In 1 blind votes, Claude Opus 4 wins 100% of the time. That's not luck.

Clear winner
Writing DNA

Style Comparison

Similarity
97%

Claude Opus 4 uses 11.2x more emoji

Grok 4.1 Fast
Claude Opus 4
67%Vocabulary64%
15wSentence Length62w
0.17Hedging0.52
4.7Bold4.4
3.7Lists9.1
0.00Emoji0.11
0.99Headings1.87
0.14Transitions0.27
Based on 24 + 16 text responses
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Grok 4.1 FastClaude Opus 4

279 AI models invented the same fake scientist.

We read every word. 250 models. 2.14 million words. This is what we found.

AI Hallucination Index 2026
Free preview13 of 58 slides
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