Telegram is currently using 87MB of my system memory on my linux box. Furthermore, under linux there is no way to minimize signal to tray, it always stays visible in task list. No thank you, but I refuse to use electron-based "native" apps.
I've been using signal for a while and I have successfully converted all my family and friends to using it. That includes a 70+ year old mother and father.
There have been no issues in using it's function from sending messages to video chat and everything in between.
One of the reasons people use Telegran (aside from chats\groups\bots) - is channel, for many people this is new RSS.
When I tried Signal, it frequently crashed, corrupted messages (requiring a reinstall of the iOS app), dropped messages, etc. As a result, all the people I persuaded to use it stopped and I currently have zero contacts on there.
I ended up preferring Matrix via Riot.im though...