Phi-3.5 Mini vs o3 Pro
Compare Phi-3.5 Mini and o3 Pro: pricing, performance, context window, latency, and best use cases. Side-by-side comparison on XALEN.
Updated 2026-05-21 · By Abhishek Raj · Our methodology
| Feature | Phi-3.5 Mini | o3 Pro |
|---|---|---|
| Category | Compact | Reasoning |
| Parameters | 3.8B | ~1T |
| Context Window | 128K | 200K |
| Input Price | $0.005/1M tokens | $0.15/1M tokens |
| Output Price | $0.01/1M tokens | $0.60/1M tokens |
| Latency | ~50ms | ~5000ms |
Choose Phi-3.5 Mini when:
- ✓ Simple Q&A
- ✓ Classification
- ✓ Edge inference
128K context in tiny model, Ultra-low cost, Fast
Choose o3 Pro when:
- ✓ Research-grade reasoning
- ✓ Mathematical proofs
- ✓ Hardest problems
Deepest reasoning, Best for hard problems, Highest accuracy
Verdict: Phi-3.5 Mini vs o3 Pro
For cost efficiency, Phi-3.5 Mini wins at $0.005/1M input tokens. For speed, o3 Pro is faster at ~5000ms. Phi-3.5 Mini excels at Simple Q&A while o3 Pro is better for Research-grade reasoning. 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. o3 Pro costs $0.15 input and $0.60 output. Phi-3.5 Mini is 30.0x 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. o3 Pro offers 200K context at ~5000ms. o3 Pro has the larger context window.
Best For
Phi-3.5 Mini (Compact) is optimized for: Simple Q&A, Classification, Edge inference. o3 Pro (Reasoning) works best for: Research-grade reasoning, Mathematical proofs, Hardest problems.
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 o3 Pro
response_b = client.chat.completions.create(
model="o3-pro",
messages=[{"role": "user", "content": "Your question here"}]
)Frequently Asked Questions
Which is better, Phi-3.5 Mini or o3 Pro?
Phi-3.5 Mini (Compact, 3.8B) offers 128K context in tiny model. o3 Pro (Reasoning, ~1T) offers Deepest reasoning. Choose Phi-3.5 Mini for Simple Q&A or o3 Pro for Research-grade reasoning.
How much does Phi-3.5 Mini cost vs o3 Pro?
Phi-3.5 Mini: $0.005/1M input, $0.01/1M output. o3 Pro: $0.15/1M input, $0.60/1M 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 o3 Pro 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.