Telegram has been criticized for its encryption algorithms but it's not completely accurate that conversations are sent unencrypted. Client-server encryption is applied by default and end-to-end encryption is optionally enabled in secret chats, at least according to their FAQ. Also I never needed official Android client to register some months ago, I don't know if this is true now.
Signal on the other hand applies end-to-end encryption by default and its protocol is considered very good but its Android client depends on Google APIs. Plus I don't want to use Chrome just to be able to have Signal on the desktop.
I looked into all this during my summer vacation and I'm still undecided.. I'd even give XMPP a try after reading this but almost none of my friends use it