On Signal, every message uses end-to-end encryption. Signal's servers can't see the messages you are sending, only you and the recipient can read them. Signal's encryption protocol is carefully scrutinized and follows best-practices.

Telegram sends messages in plain-text by default. Telegram servers have access to all plain-text messages that you send.

Telegram's private chats use end-to-end encryption. But they use an encryption protocol that they invented themselves that doesn't follow best-practices. Encryption experts have been critical of Telegram's encryption protocol since it was released. So your private messages might not be so private, either.

If you are doing something sensitive and want to stay out of prison, use Signal.

Actually, always use Signal unless you have contacts on Telegram that refuse to migrate. Consider all communication via Telegram to be on public record.

> Consider all communication via Telegram to be on public record.

Just because the protocol has flaws, doesn't mean everyone can exploit them.

On the other hand it's possible for Google to read every communication because they have root on your phone. So using Telegram [1] with a custom ROM without Google services (e. g. [2]) will make it harder for Google at least. Not easily possible with Signal.

[1] https://f-droid.org/repository/browse/?fdfilter=telegram&fdi... [2] https://copperhead.co/android/

> Telegram sends messages in plain-text by default.

This sounds like everyone has access to those messages. Better: Telegram sends messages client-server encrypted by default and since you can't run your own Telegram servers, this is a problem.