Depends on your use case. Signal is definitely more privacy focused, but telegram has more people using it and is easier for people to use and understand. Telegram is very akin to Discord, in that all the data is stored somewhere you have no control over.

The problem with this question is your friends, if whatever you decide on isn’t something your friends have or are willing to get, then it’s not useful for you. Signal offers probably the best mix of adoption and security. It however misses a few notable features, for example the iOS client has no way to back up or restore your messages. I’m a big fan of matrix, which seems very extensible and has good security, but if you are in a sensitive application like an authoritarian country, it wouldn’t be my choice. All the messages are stored on the server and while they are encrypted it’s still not what I would use for a chat I never want to see in court.

…or you go for Matrix, which has “bridges” allowing to chat with Signal and Telegram users (among others).

https://matrix.org/ecosystem/bridges/