From my experience of constantly using both, Signal's UX is inferior unfortunately. On both macOS and iOS Signal feels like a second grade cross-platform app with a clunky Android feel (no ribbon effect, no animations, poor aesthetics).

Telegram's UX quality is far superior to any other messenger app that I've ever used. Its social functions are quite nice too, I think Telegram invented some of them before they were copied by the others.

The thing with Telegram though is that you can never trust a private company if you are a journalist, dissident or a government official. We don't know whether Pavel Durov is as independent as he wants us to believe he is. The big red flag in the Telegram story is why it's still not banned or censored in Russia. We don't know.

But all in all, kudos to those who have built it, they have my respect, Telegram is one of the best pieces of software at least among the messaging apps.