ChatGPT 4o vs Claude Sonnet 4: which is better?

Both are flagship models from the two leading AI labs. They're closer in capability than benchmarks suggest, but they have genuinely different strengths:

• ChatGPT 4o: faster, more conversational, multimodal (image input). Best for: brainstorming, quick answers, casual writing, coding snippets, voice mode.
• Claude Sonnet 4: slower but more careful, longer context window, more thoughtful tone. Best for: long-form articles, document analysis, nuanced instructions, sensitive topics, multi-file coding.

The concrete numbers behind that summary: ChatGPT 4o has a 128,000-token context window against Claude Sonnet 4's 200,000, so Claude can hold roughly 150,000 words of conversation and documents in memory at once. ChatGPT 4o is natively multimodal and typically starts streaming its answer a second or two faster. In blind preference tests, Claude's prose wins more often on long-form writing while 4o wins on short conversational replies.

The honest take: if you only pick one, ChatGPT 4o is the better default for everyday questions. But for a serious writing project, Claude usually produces output that needs less editing. AskAI.free lets you ask both in the same conversation; try the same prompt in both and see which voice you prefer.

Neither model browses the web by default, both answer from training data with a fixed knowledge cutoff. For anything time-sensitive, switch to a Perplexity search model instead of trusting either of them on recent events.