What is the difference between ChatGPT-4o (March 2025) and Claude Sonnet 4.5?

ChatGPT-4o (March 2025) is developed by OpenAI while Claude Sonnet 4.5 is developed by Anthropic. ChatGPT-4o (March 2025) has a 128K token context window vs Claude Sonnet 4.5's 200K. You can compare their actual outputs across 29 challenges on Rival to see how they differ in practice.

Which is better, ChatGPT-4o (March 2025) or Claude Sonnet 4.5?

It depends on your use case. ChatGPT-4o (March 2025) and Claude Sonnet 4.5 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 29 challenges so you can judge which fits your needs best.

How much does ChatGPT-4o (March 2025) cost compared to Claude Sonnet 4.5?

ChatGPT-4o (March 2025) costs $5/M input tokens and Claude Sonnet 4.5 costs $3/M input tokens. Claude Sonnet 4.5 is $2.00/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

How can I compare ChatGPT-4o (March 2025) and Claude Sonnet 4.5 on Rival?

This page shows a side-by-side comparison of ChatGPT-4o (March 2025) and Claude Sonnet 4.5 across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

Updated Sep 2025

ChatGPT-4o (March 2025)vsClaude Sonnet 4.5

Claude Sonnet 4.5 is cheaper than ChatGPT-4o (March 2025) at $3/M vs $5/M input tokens.

ChatGPT-4o (March 2025) and Claude Sonnet 4.5 compared across 29 shared prompts
Spec	ChatGPT-4o (March 2025)	Claude Sonnet 4.5
Input price	$5/M tokens	$3/M tokens
Output price	$15/M tokens	$15/M tokens
Context window	128K tokens	200K tokens
Weights	—	Closed
Free API (OpenRouter)	No	No
Released	Mar 2025	Sep 2025