OpenAI o3 vs Claude Opus 5.5: Which AI Model Should You Choose?

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.RAILWAIL_API_KEY,
  baseURL: "https://railwail.com/v1",
});

// Before — using OpenAI o3
let r = await client.chat.completions.create({
  model: "o3",
  messages: [{ role: "user", content: "Hello" }],
});

// After — switched to Claude Opus 5.5
r = await client.chat.completions.create({
  model: "claude-opus-5-5",
  messages: [{ role: "user", content: "Hello" }],
});

from openai import OpenAI

client = OpenAI(
    api_key=os.environ["RAILWAIL_API_KEY"],
    base_url="https://railwail.com/v1",
)

# Before — using OpenAI o3
r = client.chat.completions.create(
    model="o3",
    messages=[{"role": "user", "content": "Hello"}],
)

# After — switched to Claude Opus 5.5
r = client.chat.completions.create(
    model="claude-opus-5-5",
    messages=[{"role": "user", "content": "Hello"}],
)

# Before — using OpenAI o3
curl https://railwail.com/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "o3",
    "messages": [{"role": "user", "content": "Hello"}]
  }'

# After — switched to Claude Opus 5.5
curl https://railwail.com/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-opus-5-5",
    "messages": [{"role": "user", "content": "Hello"}]
  }'