[Bladtman]

Telegram rolls their own non-standard crypto protocol as I understand it. This is a bit of a no-no when it comes to security. More importantly; chat's arent' end-to-end encrypted by default (I can't find a way to enable it in the web-app), which means the telegram-whatsapp comparison makes no sense. Whatsapp is secure, telegram is not.

[Bladtman]

Also; end-to-end encrypted chats in telegram (they call them "secret chats") won't follow you between devices. A secret chat started on one device, won't be accessible from another. This makes them far less useful, and dissuades users from using them. Again; comparing whatsapp to telegram in terms of security is apples vs oranges.