Really, telegram is being naked for 99% of the time, with an optional clothes feature that is limited and mobile only. Whereas signal is fully dressed, all the time.
Signal is 100% encrypted, all groups encrypted, all messages encrypted, all contacts encrypted. The vendor knows when your registered… that is all.
Of course people who don’t understand the sheer dystopia of cleartext coms and visible social graphs — They will say “when I need them “ I will encrypt. No, you must encrypt all the time. Messages must be indistinguishable. You don’t just encrypt the sensitive stuff, you should encrypt everything!
In other words, you want your chats with news and memes E2E by default, so when you chat about something sensitive you a) don't have to do anything, b) won't forget about it until it's too late and c) won't give away the fact that this particular conversation suddenly went private.
Telegram management is weirdly stubborn af in this regard. Which could be either "we know better" syndrome, simple ignorance, or even malice. They, however, undeniably know their ways with UX and marketing, so, once again, as in an old Russian proverb, we end up with a barrel of honey, with a spoonful of tar - the nicest-looking but crappily implemented tech always wins.
In my case it is not rare to prefer my conversations not to be stored in plaintext on someone else's computer
Signal is good for E2E but not comparable in terms of convenience.