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.
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.