I have used both Signal and Telegram for years and I'm not seeing much UX difference. What's better for you on Telegram?
To be fair, Signal has gotten a lot better and a lot easier to show people how to sign up. Back when I did my migration off FB Messenger it was a different story and Telegram was basically on par with Messenger
Right clicking on a conversation on signal does nothing. On telegram is shows the menu that if expect.
Signal takes many seconds to render the main window. Telegram opens in a reasonable amount of time.
Chat bubbles in signal reveal some hidden icons when you hover them, but have a separate right click menu when you click them. You basically have to guess which of both menus contains the action that you need.
Copy paste of images often doesn’t work on Signal. The voice clip button does nothing. It simply doesn’t work, but doesn’t show any errors or log anything.
I want to like Signal, but the clients are simply terrible, have bad UX and are full of bugs.