GPT-5.3 Codex vs Llama 3.1 405B

Side-by-side benchmark comparison across knowledge, coding, math, and reasoning.

Quick Verdict

GPT-5.3 Codex wins overall with a score of 85 vs 58 (27 point difference).GPT-5.3 Codex wins 4 out of 4 categories.

Knowledge

GPT-5.3 Codex

GPT-5.3 Codex

96

Llama 3.1 405B

68.5

99
MMLU
70
97
GPQA
70
95
SuperGPQA
68
93
OpenBookQA
66

Coding

GPT-5.3 Codex

GPT-5.3 Codex

95

Llama 3.1 405B

62

95
HumanEval
62

Mathematics

GPT-5.3 Codex

GPT-5.3 Codex

97.1

Llama 3.1 405B

69

99
AIME 2023
70
99
AIME 2024
72
98
AIME 2025
71
95
HMMT Feb 2023
66
97
HMMT Feb 2024
68
96
HMMT Feb 2025
67
96
BRUMO 2025
69

Reasoning

GPT-5.3 Codex

GPT-5.3 Codex

94

Llama 3.1 405B

67

95
SimpleQA
68
93
MuSR
66

Frequently Asked Questions

Which is better, GPT-5.3 Codex or Llama 3.1 405B?

GPT-5.3 Codex scores higher overall with 85 vs 58, a difference of 27 points across all benchmarks.

Which is better for knowledge tasks, GPT-5.3 Codex or Llama 3.1 405B?

GPT-5.3 Codex leads in knowledge tasks with an average score of 96 vs 68.5.

Which is better for coding, GPT-5.3 Codex or Llama 3.1 405B?

GPT-5.3 Codex leads in coding with an average score of 95 vs 62.

Which is better for math, GPT-5.3 Codex or Llama 3.1 405B?

GPT-5.3 Codex leads in math with an average score of 97.1 vs 69.

Which is better for reasoning, GPT-5.3 Codex or Llama 3.1 405B?

GPT-5.3 Codex leads in reasoning with an average score of 94 vs 67.