Telegram also has native, non-Electron apps, for many platforms, could it be an advantage? It also has convenient public chats and "channels" (microblogs). It has support for proxy servers, allows sharing proxy servers and has traffic obfuscation which Signal (I assume) doesn't have.

But for me Telegram and Signal are equally insecure because they don't allow anonymous accounts without a phone number. Using phone number for authentication is insecure because it is very easy to intercept SMS messages, especially if you are a telecom or the government. You better avoid using such messengers and not support them unless you want to provide your ID in future for registration on any website.