This is false. No proposed ads in 1:1 or any size group chats, only large channels (which are like RSS feeds, you can join but not post).

In addition 100% of Telegram traffic is encrypted over the wire (like this website, your bank, etc). The only difference with secret chats is that they're end to end encrypted.

Signal is a very bad user experience if you use several devices (phone, tablet, home computer, work computer). Continuing a chat on a different device doesn't work nearly as well as on Telegram where it's flawless.