Can I use only one of them?

Yes. If you only write, ChatGPT is enough. If you only need a figure or a date, Perplexity is enough. The failure is using one chat for both and never opening sources.

Which one is the better «AI search»?

Perplexity presents itself as an answer with citations. ChatGPT with search also cites, but the default habit is drafting. Pick by the deliverable, not the marketing.

When the piece is long and voice matters, Claude usually beats both as an editor. It does not replace Perplexity for opening sources.

ChatGPT vs Perplexity

Write and think in a chat, or brief with citations. They do not replace the same step.

	ChatGPT	Perplexity
Best for	Drafting, ideation and a flow you repeat	A bounded question with citations you can open
Sources	Optional search; you must ask it to flag uncertainty	Citations in the answer; the work is opening two of them
Prose	Very high if the brief is good	Fine; it is not an editor
Risk	Fluent text that invents smoothly	A summary that looks like a primary source and is not
When to switch	When you already have facts and need the deliverable	When you still do not know what is backed
Entry plan	Free + Plus / Team	Free + Pro

Verdict

Use Perplexity to bound facts and open sources. Move to ChatGPT (or Claude) when you need to draft, vary tone or keep a repeatable flow. If you paste Perplexity's paragraph into a report, you are publishing an intermediary.