What's the difference between a fiat and a ferrari? What's the difference between CentOS and Linux Mint? What's the difference between a macdonalds and a michelin burger?
I have friends and groups on both platforms. On Signal, I'm basically just sending messages (and only unimportant one, like, when are we meeting. Sending media mostly sucks so I generally only have very dry chats on Signal).
Whereas on Telegram, I'm having fun. In fact it's so versatile, that my wife and I use it as a collaborative note-taking system, archiver, cvs, live shopping list, news app (currently browsing hackernews from telegram), etc. We basically have our whole life organised via Telegram. I lose count of all the features I use effortlessly on a daily basis, and only realise it when I find myself on another app. This is despite the fact that both Signal and whatsapp have since tried to copy some of these features, because they do so badly. A simple example that comes to mind: editing messages. It took years for whatsapp to be able to edit a message (I still remember the old asterisk etiquette to indicate you were issuing a correction to a previous message). Now you can, but it's horrible ux; I think you long press and then there's a button next to copy which opens a menu where you find a pencil which means edit, or sth like that. In telegram I don't even remember how you do it, because it's so intuitive that I don't have to.
Perhaps that's why I find the whole "Telegram encryption" discussion baffling to be honest. For me, it's just one of Telegram's many extra features you can use. You don't have to use it, but it's there if you want to. I don't feel like Telegram has ever tried to mislead its users that it's raison d'etre is for it to be a secret platform only useful if you're a terrorist (like the UK government seems to want to portray it recently).
I get the point about "encryption by default", but this doesn't come for free, there are usability sacrifices that come with it, and not everyone cares for it. Insisting that not having encryption by default marrs the whole app sounds similar to me saying not having a particular set of emojis set as the default marrs the whole app. It feels disingenuous somehow.