Signal does not have an official Signal CLI (or method of creating integrations) so users are compromising their use of Signal by using heavily patched and out-of-date code written by unknown third parties.
Telegram has support for integrations and clients but isn't a service anyone should trust.
Telegram offering bells and whistles that leaks everything to the service provider is not an argument for Telegram the same way "it launches the video game" isn't an argument for video game cracks that carry ransomware.
Both are called Trojan Horses and are considered malware.
Signal does not have an official Signal CLI (or method of creating integrations) so users are compromising their use of Signal by using heavily patched and out-of-date code written by unknown third parties.
Telegram has support for integrations and clients but isn't a service anyone should trust.