Short answer: they overlap 90%, and the free tiers of both will teach you more than any comparison article.
Where they genuinely differ: ChatGPT is the swiss-army knife — voice conversations, image generation, a massive plugin/app ecosystem, and the most polished mobile experience. Claude pulls ahead on long documents (contracts, reports, books), writing that sounds like a person wrote it, and analysis where being right matters more than being fast. It also has the stronger privacy posture of the two.
The honest advice nobody selling subscriptions gives: use both free for a week on your real tasks, then pay for the one you kept coming back to. See the full head-to-head, or take the quiz to see which fits your situation.