Llama 3.1 405B VS ChatGPT-4o

2025-12-20

In the rapidly evolving landscape of Large Language Models (LLMs), the rivalry between Meta's Llama 3.1 405B and OpenAI's GPT-4o represents the pinnacle of generative AI technology. This comprehensive analysis dives deep into the technical specifications, performance benchmarks, and real-world practical tests of these two titans based on the original data from Benchmarks and specs.

"The competition between language models is intense... this iteration of models certainly stole even more spotlight from OpenAI."

Core Specifications Comparison

Specification Llama 3.1 405B ChatGPT-4o
Context Window 128K 128K
Output Tokens 4K 16K
Parameters 405B Unknown (Proprietary)
Knowledge Cutoff Dec 2023 Oct 2023
Speed (Tokens/sec) ~29.5 t/s ~103 t/s

While both models share a 128K context window, GPT-4o significantly leads in inference speed, clocking in at nearly 3.5x the speed of Llama 3.1 405B. However, Llama's open-weights nature provides a level of transparency and local deployability that GPT-4o lacks.

Standardized Benchmarks

Benchmarks offer a standardized way to measure "intelligence" across various domains. Here is how they stack up:

Benchmark Topic Llama 3.1 405B ChatGPT-4o
MMLU (General Knowledge) 88.6 88.7
Human Eval (Coding) 89.0 90.2
MATH (Advanced Math) 73.8 70.2
DROP (Reasoning) 84.8 83.4

Head-to-Head Practical Tests

🚀 Test 1: Strict Constraint Adherence

Prompt: Create 10 sentences with exactly 7 words each.

  • Llama 3.1 405B: 10/10 Score. Perfectly followed the word count constraint for every sentence.
  • GPT-4o: 8/10 Score. Failed on two sentences, likely miscounting "the" or small stop-words.

🧠 Test 2: Mathematical Logic

Scenario: Maximizing the volume of a cone inscribed in a sphere of radius R.

Llama 405B Result: Correct ($h = \frac{4}{3}R$). The model successfully derived the volume function and used differentiation to find the extremum.

GPT-4o Result: Incorrect ($h = \frac{2R}{\sqrt{3}}$). While the reasoning started strong, it faltered in the final calculation steps.

💻 Test 3: Coding Ability (Python/Pygame)

Both models were asked to build a functional Arkanoid game. The results were nuanced:

Llama 3.1 405B Good logic, but occasional "collision physics" bugs where the ball passed through textures.
GPT-4o Superior physics and ball interaction, but the code included a game-breaking crash on the "Game Over" screen.

Try It Yourself: Python Comparison Snippet

Use the following code to run your own side-by-side comparison using the AIML API:

import openai

def main(): client = openai.OpenAI( api_key='', base_url="https://api.aimlapi.com", )

models = ['meta-llama/Meta-Llama-3.1-405B-Instruct-Turbo', 'gpt-4o']
prompt = 'Explain the Quantum Hall Effect in 3 sentences.'

for model in models:
    response = client.chat.completions.create(
        model=model,
        messages=[{'role': 'user', 'content': prompt}]
    )
    print(f"--- {model} ---")
    print(response.choices[0].message.content + "\n")
if name == "main": main() 

Cost-Efficiency Analysis

Economic Insight: Llama 3.1 405B offers a massive advantage in output costs. While input pricing is competitive, the output price for Llama is roughly 3x cheaper than GPT-4o, making it the superior choice for long-form content generation.

The Verdict

Choose Llama 3.1 405B if:

  • You need cost-effective high-volume output.
  • Strict adherence to formatting constraints is required.
  • You prefer an open-weights ecosystem.

Choose GPT-4o if:

  • Speed is your primary concern (Real-time apps).
  • You need larger output token buffers (16K).
  • You require highly polished UI/Physics in code generation.

Frequently Asked Questions (FAQ)

Q1: Is Llama 3.1 405B really as smart as GPT-4o?

A: Yes. In many reasoning and mathematical benchmarks, Llama 3.1 405B matches or even slightly exceeds GPT-4o's performance. However, GPT-4o remains faster in response time.

Q2: Which model is better for coding?

A: It is a draw. GPT-4o tends to write more robust interaction logic, while Llama 3.1 405B often follows complex architectural instructions with fewer crashes, despite minor physics glitches.

Q3: How much can I save using Llama 3.1 405B?

A: For token-heavy tasks (like writing books or long reports), Llama 3.1 405B can be up to 66% cheaper on output costs compared to GPT-4o via most API providers.

Q4: Can Llama 3.1 405B handle images like GPT-4o?

A: GPT-4o is a native multimodal model. While Llama 3.1 405B is primarily focused on text and reasoning, it can be integrated into multimodal workflows, but GPT-4o currently holds the edge in native vision tasks.