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	A 150-word email, three headline variants, an internal brief you repeat every Tuesday	«What does X's official documentation say about Y?» with 3 links you open
Sources	Optional search; ask it to «mark [?] anything not in my notes»	Citations in the answer; open at least two and check date and author
Prose	High if the brief has format, audience and a word limit	Fine for summarising; it does not replace a long-form tone editor
Risk	An invented figure that sounds precise («23 % of…»)	A summary you cite as if it were the original paper
When to switch	When you already have 3 verified facts and need the final paragraph	When you still do not know whether the figure has a primary source
Entry plan	Free + Plus / Team (chatgpt.com)	Free + Pro (perplexity.ai)

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.