GPT-5 vs Claude Sonnet 4.5: Latency Benchmarks

In production environments, latency matters as much as model quality. We ran 10,000+ requests through both GPT-5 and Claude Sonnet 4.5 to understand their performance characteristics under real-world conditions.

Key Findings

Verdict: Claude Sonnet 4.5 delivers 3.5x faster median response times while maintaining comparable output quality.

Test Methodology

We used Transend AI's unified API to ensure fair comparison:

const benchmark = async (model: string) => {
  const start = performance.now();

  await fetch("https://api.transendai.net/v1/texts/chat/completions", {
    method: "POST",
    headers: {
      "Authorization": `Bearer ${process.env.TRANSEND_API_KEY}`,
      "Content-Type": "application/json"
    },
    body: JSON.stringify({
      model,
      messages: [
        { role: "system", content: "You are a concise assistant." },
        { role: "user", content: "Explain quantum computing in 3 sentences." }
      ]
    })
  });

  return performance.now() - start;
};

Variables Controlled

• Region: US-East-1 (Virginia)
• Time of Day: Distributed across 24h
• Prompt Complexity: 3 tiers (simple, medium, complex)
• Token Limits: Fixed at 500 max tokens

Latency Distribution

Simple Prompts (< 50 tokens)

GPT-5 Pro:

• P50: 4.2s
• P95: 8.1s

Claude Sonnet 4.5:

• P50: 1.3s
• P95: 2.4s

Complex Prompts (200+ tokens)

GPT-5 Pro:

• P50: 11.8s
• P95: 18.6s

Claude Sonnet 4.5:

• P50: 3.7s
• P95: 6.2s

When to Use Each Model

Choose GPT-5 Pro if:

• You need cutting-edge reasoning (math, code, logic)
• Output quality > speed
• Handling multi-step agent workflows

Choose Claude Sonnet 4.5 if:

• Latency is critical (chatbots, live support)
• High-throughput batch processing
• Cost-sensitive workloads (Claude is ~20% cheaper)

Edge Routing Impact

Transend AI's smart edge routing reduced latency by an additional 25-40% compared to direct provider APIs:

This is achieved through:

• Global POPs (30+ regions)
• Connection pooling and HTTP/2 multiplexing
• Automatic failover to backup regions

Production Recommendations

1. Use Claude for user-facing chat — Sub-2s responses feel instant
2. Route complex reasoning to GPT-5 — Worth the wait for accuracy
3. Enable Transend AI's fallback — Auto-retry on provider downtime
4. Monitor P95, not P50 — Tail latency kills UX

Try It Yourself

# Install Transend AI SDK
npm install @transend/ai-sdk

# Run your own benchmark
npx transend benchmark --models gpt-5-pro,claude-sonnet-4.5

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Updated: March 2025 Tested with: GPT-5 Pro (Dec 2024), Claude Sonnet 4.5 (Feb 2025)