Saw someone ask a question why is Signal better than Telegram, found this reddit thread and someone did a great job with a summary.
If it ever gets deleted, here’s a copy:
Nothing is stored on Signal's servers, all data lives on your own device(s) and only you hold the encryption keys; Telegram stores everything you do in plaintext on their servers and they hold the encryption keys. That is why pulling down data on a new device is fast.Signal encrypts everything you do end-to-end by default no matter what device you’re using it on; Telegram’s encryption is opt-in, only works on mobile, and only in one-to-one conversations
Signal’s encryption is the gold-standard, and universally praised by Cybersecurity experts; Telegram “rolled their own” encryption, a giant red flag in Cybersecurity, and the quality of their encryption is not nearly as high. Telegram’s encryption has been called “weird” by Cybersecurity experts because it was not created by trained Cryptographers
Signal’s Android, iOS, Desktop, and Server code is open-source; only Telegram’s client code is open-source, so there’s no telling what they’re doing with the data they store on their servers
Signal is a registered non-profit charity; Telegram is now profit-driven after years of being free which means they will inevitably start selling user data - die a hero, or live long enough to become the villain
Signal has never been banned in Russia and then suddenly unbanned for no reason; Telegram was banned in Russia until it was unbanned, seemingly with no reason or explanation