Llama 3.1 405B vs OpenAI o3

Compare Llama 3.1 405B by Meta AI against OpenAI o3 by OpenAI, tested across 7 shared challenges. Updated April 2026.

Which is better, Llama 3.1 405B or OpenAI o3?

Llama 3.1 405B and OpenAI o3 are both competitive models. Llama 3.1 405B costs $2.7/M input tokens vs $10/M for OpenAI o3. Compare their real outputs side by side below.

Key Differences Between Llama 3.1 405B and OpenAI o3

Llama 3.1 405B is made by meta while OpenAI o3 is from openai. On pricing, Llama 3.1 405B costs $2.7/M input tokens vs $10/M for OpenAI o3.

Our Verdict
Llama 3.1 405B
Llama 3.1 405B
OpenAI o3
OpenAI o3

No community votes yet. On paper, these are closely matched - try both with your actual task to see which fits your workflow.

Llama 3.1 405B is 13x cheaper per token — worth considering if cost matters.

Too close to call
Writing DNA

Style Comparison

Similarity
69%

OpenAI o3 uses 69.5x more bold

Llama 3.1 405B
OpenAI o3
56%Vocabulary68%
15wSentence Length14w
0.41Hedging0.26
0.0Bold0.7
1.9Lists3.0
0.03Emoji0.00
0.00Headings0.38
0.16Transitions0.12
Based on 5 + 16 text responses
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Llama 3.1 405BOpenAI o3

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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