Are screenshots useless?

No. They're fast, they show the chat exactly as it looked on the screen, and they're the only option for view-once media you saw. They just don't replace the conversation as a whole.

What does an export have that screenshots don't?

Every message in the period, in order, with exact dates and times, the original photos and voice note files, and searchable text, without gaps between screens.

Which one will a court or authority prefer?

That depends on the case and the country. Many lawyers ask for both. Ask one where you are.

WhatsApp Export vs Screenshots: Which to Keep for a Dispute

Screenshots are quick, but they show a few screens, lose voice notes and leave gaps. What a chat export keeps that screenshots don't, when screenshots still help, and how to keep both properly.

A WhatsApp export laid out as a chronological document

When a conversation turns into a dispute, the reflex is to screenshot it. Screenshots are fine for showing one moment. They’re a poor way to keep a whole conversation, and the gaps are exactly what the other side will point at.

What screenshots do well #

Instant. No settings, no files to unzip.
Visual. They show the chat as it looked, with names, ticks and layout.
Sometimes the only option. A view-once photo you saw, or a chat where export is blocked.

Where screenshots fall short #

Gaps. Twenty screenshots of a 2,000-message chat leave out almost everything, and nothing shows that a screen was skipped.
Voice notes are invisible. A screenshot shows a play button, not what was said.
Photos are thumbnails. The original image, with its full resolution, isn’t in the screenshot.
Hard to search and quote. It’s an image, not text.
Easy to question. A screenshot can be cropped or edited, and on its own it shows nothing around the message.

What an export keeps #

A chat export with media gives you:

every message in the period, in order, with date, time and sender;
the original photos, videos and documents as files;
every voice note as an audio file;
searchable text.

Its limits are worth knowing too: at most the 10,000 most recent messages with media (40,000 without), and no view-once or vanished messages. See WhatsApp export limit.

The sensible approach: keep both #

Export the chat with media and keep the .zip unchanged (Android, iPhone).
Screenshot the key moments as well, with the date header visible.
Keep the phone and the chat. Don’t delete anything.
Make it readable. Turn the export into a document someone can read and refer to by page.

Zap2Doc does step 4: a chronological PDF with photos in place, voice notes transcribed under each message and numbered pages. You see a free preview before paying. How a court or authority wants material submitted varies; ask a lawyer where you are. More in how to present a WhatsApp chat as evidence.