OpenAI vs Anthropic in 2026: A Side-by-Side Comparison
By Promptster Team · 2026-03-04
The two most popular AI providers — OpenAI and Anthropic — have both shipped major model updates in early 2026. But which one should you use? The answer, as always, depends on your use case.
We ran both providers through Promptster with identical prompts across three categories: coding, creative writing, and multi-step reasoning. Here's what we found.
Test Setup
All tests used the same configuration:
- OpenAI: GPT-4o (latest)
- Anthropic: Claude Sonnet 4.5
- Temperature: 0.7 (default)
- Max tokens: 2,000
Each prompt was run 5 times to account for variance, and we averaged the results.
Coding Tasks
We tested with three coding prompts of increasing complexity:
# Prompt 1: Simple function
"Write a Python function that finds all prime numbers up to n using the Sieve of Eratosthenes."
# Prompt 2: Data structure
"Implement a thread-safe LRU cache in Python with O(1) get and put operations."
# Prompt 3: System design
"Write a rate limiter middleware for Express.js using the sliding window algorithm with Redis."
Results
| Metric | GPT-4o | Claude Sonnet 4.5 |
|---|---|---|
| Avg response time | 2.1s | 2.8s |
| Code correctness | 4.8/5 | 4.9/5 |
| Code readability | 4.5/5 | 4.8/5 |
| Avg cost per prompt | $0.008 | $0.011 |
Winner: Tie. GPT-4o was faster and cheaper, Claude produced slightly more readable code with better comments. Both achieved near-perfect correctness.
Creative Writing
We tested with prompts ranging from short-form to long-form creative tasks:
- "Write a haiku about debugging code at 3am"
- "Write a product launch email for a developer tool that helps compare AI models"
- "Write the opening chapter of a mystery novel set in a quantum computing lab"
Results
| Metric | GPT-4o | Claude Sonnet 4.5 |
|---|---|---|
| Avg response time | 3.4s | 4.1s |
| Creativity | 4.2/5 | 4.6/5 |
| Coherence | 4.7/5 | 4.8/5 |
| Following instructions | 4.8/5 | 4.7/5 |
Winner: Claude Sonnet 4.5 for creative tasks. More vivid language, better narrative structure, and more surprising word choices. GPT-4o was more formulaic but followed instructions slightly more precisely.
Multi-Step Reasoning
We tested with logic puzzles, math word problems, and chain-of-thought reasoning:
- "A farmer has 17 sheep. All but 9 die. How many are left?"
- "If it takes 5 machines 5 minutes to make 5 widgets, how long does it take 100 machines to make 100 widgets?"
- Complex scheduling optimization problem
Results
| Metric | GPT-4o | Claude Sonnet 4.5 |
|---|---|---|
| Avg response time | 1.8s | 2.3s |
| Correct answer | 4.6/5 | 4.7/5 |
| Explanation quality | 4.3/5 | 4.8/5 |
Winner: Claude Sonnet 4.5 by a small margin. Better step-by-step explanations and fewer "gotcha" failures on trick questions.
Cost Comparison
Over our full test suite (15 prompts x 5 runs each):
| GPT-4o | Claude Sonnet 4.5 | |
|---|---|---|
| Total cost | $0.89 | $1.24 |
| Cost per 1K tokens (input) | $0.0025 | $0.003 |
| Cost per 1K tokens (output) | $0.01 | $0.015 |
GPT-4o is roughly 30% cheaper at current pricing.
Our Recommendation
- For coding: Either works well. Choose GPT-4o if speed matters, Claude if you value code documentation.
- For creative writing: Claude Sonnet 4.5 has the edge.
- For reasoning: Claude Sonnet 4.5, especially for explanations.
- For cost-sensitive workloads: GPT-4o.
The best approach? Test with your own prompts. These benchmarks reflect general tendencies, but your specific use case may yield different results.
Try It Yourself
Run this exact comparison in Promptster — select both providers, paste your prompt, and see the results side by side in seconds. No need to trust benchmarks when you can generate your own data.