Llama 3.1 405B vs Gemini 2.5 Pro Preview

Compare Llama 3.1 405B and Gemini 2.5 Pro Preview: pricing, performance, context window, latency, and best use cases. Side-by-side comparison on XALEN.

Updated 2026-05-21 · By Abhishek Raj · Our methodology

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Feature Llama 3.1 405B Gemini 2.5 Pro Preview
CategoryOpen SourceFrontier
Parameters405B~1.5T
Context Window128K2M
Input Price$0.08/1M tokens$0.07/1M tokens
Output Price$0.14/1M tokens$0.21/1M tokens
Latency~600ms~700ms

Choose Llama 3.1 405B when:

  • ✓ Premium tasks
  • ✓ Research
  • ✓ Fine-tuning base
Key Strengths:

Largest open model, Highest open-source quality

Choose Gemini 2.5 Pro Preview when:

  • ✓ Research
  • ✓ Long analysis
  • ✓ Testing new capabilities
Key Strengths:

2M context, Experimental features, Strong reasoning

Verdict: Llama 3.1 405B vs Gemini 2.5 Pro Preview

For cost efficiency, Gemini 2.5 Pro Preview wins at $0.07/1M input tokens. For speed, Llama 3.1 405B is faster at ~600ms. Llama 3.1 405B excels at Premium tasks while Gemini 2.5 Pro Preview is better for Research. Both are available on XALEN through a single API — try them in the Playground to see which fits your workload.

Detailed Analysis

Pricing Comparison

Llama 3.1 405B costs $0.08/1M input tokens and $0.14/1M output tokens. Gemini 2.5 Pro Preview costs $0.07 input and $0.21 output. Gemini 2.5 Pro Preview is 1.1x cheaper on input tokens. XALEN offers batch processing at 50% discount on both models.

Performance & Context

Llama 3.1 405B has a 128K context window with ~600ms latency. Gemini 2.5 Pro Preview offers 2M context at ~700ms. Gemini 2.5 Pro Preview has the larger context window.

Best For

Llama 3.1 405B (Open Source) is optimized for: Premium tasks, Research, Fine-tuning base. Gemini 2.5 Pro Preview (Frontier) works best for: Research, Long analysis, Testing new capabilities.

Try Both on XALEN

Both models are available through XALEN's OpenAI-compatible API. Switch between them by changing the model parameter:

from xalen import XALEN

client = XALEN(api_key="xln_test_YOUR_KEY")

# Use Llama 3.1 405B
response_a = client.chat.completions.create(
    model="llama-3-1-405b",
    messages=[{"role": "user", "content": "Your question here"}]
)

# Use Gemini 2.5 Pro Preview
response_b = client.chat.completions.create(
    model="gemini-2-5-pro-preview",
    messages=[{"role": "user", "content": "Your question here"}]
)

Start Building with XALEN

200+ AI models. One API. Pay-as-you-go.

Get API Key Try in Playground

Frequently Asked Questions

Which is better, Llama 3.1 405B or Gemini 2.5 Pro Preview?

Llama 3.1 405B (Open Source, 405B) offers Largest open model. Gemini 2.5 Pro Preview (Frontier, ~1.5T) offers 2M context. Choose Llama 3.1 405B for Premium tasks or Gemini 2.5 Pro Preview for Research.

How much does Llama 3.1 405B cost vs Gemini 2.5 Pro Preview?

Llama 3.1 405B: $0.08/1M input, $0.14/1M output. Gemini 2.5 Pro Preview: $0.07/1M input, $0.21/1M output. Both available on XALEN with batch processing at 50% discount.

Can I use both models on XALEN?

Yes. XALEN provides 200+ models through a single OpenAI-compatible API. Switch between Llama 3.1 405B and Gemini 2.5 Pro Preview by changing the model parameter. No code changes needed.

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Last updated: 2026-05-21. Pricing and specifications may change. Check pricing page for latest rates.