Phi-3.5 Mini vs InternLM 2.5 20B

Compare Phi-3.5 Mini and InternLM 2.5 20B: 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 Phi-3.5 Mini InternLM 2.5 20B
CategoryCompactOpen Source
Parameters3.8B20B
Context Window128K256K
Input Price$0.005/1M tokens$0.02/1M tokens
Output Price$0.01/1M tokens$0.04/1M tokens
Latency~50ms~180ms

Choose Phi-3.5 Mini when:

  • ✓ Simple Q&A
  • ✓ Classification
  • ✓ Edge inference
Key Strengths:

128K context in tiny model, Ultra-low cost, Fast

Choose InternLM 2.5 20B when:

  • ✓ Long context tasks
  • ✓ Research
  • ✓ Multilingual
Key Strengths:

256K context, Strong reasoning, Good multilingual

Verdict: Phi-3.5 Mini vs InternLM 2.5 20B

For cost efficiency, Phi-3.5 Mini wins at $0.005/1M input tokens. For speed, InternLM 2.5 20B is faster at ~180ms. Phi-3.5 Mini excels at Simple Q&A while InternLM 2.5 20B is better for Long context tasks. Both are available on XALEN through a single API — try them in the Playground to see which fits your workload.

Detailed Analysis

Pricing Comparison

Phi-3.5 Mini costs $0.005/1M input tokens and $0.01/1M output tokens. InternLM 2.5 20B costs $0.02 input and $0.04 output. Phi-3.5 Mini is 4.0x cheaper on input tokens. XALEN offers batch processing at 50% discount on both models.

Performance & Context

Phi-3.5 Mini has a 128K context window with ~50ms latency. InternLM 2.5 20B offers 256K context at ~180ms. InternLM 2.5 20B has the larger context window.

Best For

Phi-3.5 Mini (Compact) is optimized for: Simple Q&A, Classification, Edge inference. InternLM 2.5 20B (Open Source) works best for: Long context tasks, Research, Multilingual.

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 Phi-3.5 Mini
response_a = client.chat.completions.create(
    model="phi-3-5-mini",
    messages=[{"role": "user", "content": "Your question here"}]
)

# Use InternLM 2.5 20B
response_b = client.chat.completions.create(
    model="internlm-2-5-20b",
    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, Phi-3.5 Mini or InternLM 2.5 20B?

Phi-3.5 Mini (Compact, 3.8B) offers 128K context in tiny model. InternLM 2.5 20B (Open Source, 20B) offers 256K context. Choose Phi-3.5 Mini for Simple Q&A or InternLM 2.5 20B for Long context tasks.

How much does Phi-3.5 Mini cost vs InternLM 2.5 20B?

Phi-3.5 Mini: $0.005/1M input, $0.01/1M output. InternLM 2.5 20B: $0.02/1M input, $0.04/1M 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 Phi-3.5 Mini and InternLM 2.5 20B 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.