I'm still not sure which one is better: Signal or Telegram.
The way Signal tackles the problems is smart gradual development and they are the closest to making the holy grail - e2e encryption without users even noticing it. There are no "secure" and "not secure" messages in signal - it is all encrypted and you can't turn it off. That's awesome.
Signal is more secure, yes. However its UI, UX, accessibility, feature sets and performance are absolutely in baby shoes.
You're better off with Matrix/Riot or XMPP. Neither requires a phone number, both offer the ability to communicate securely, even with a compromised server. Both also support multiple devices, group chats and federation.
Signal periodically sends truncated cryptographically hashed phone numbers for contact discovery. Names are never transmitted, and the information is not stored on the servers. The server responds with the contacts that are Signal users and then immediately discards this information. Your phone now knows which of your contacts is a Signal user and notifies you if your contact just started using Signal.
However; I don't know if their server is peer-reviewed on a regulary basis, nor do i know if the software (besides the used ciphers) is also peer-reviewed. Can't find anything on it.
I use Tox with my geek friends and Telegram with my less geek friends. I also plan to give a try to ring.cx
The gcm dependency was removed 10 months ago: https://github.com/WhisperSystems/Signal-Android/commit/1669...
You can get the apk outside of gplay on their website: https://signal.org/android/apk/