My personal experience is that I moved some friends to Telegram and kept family in WhatsApp.The time using the phone decreased, I found having 2 messengers more beneficial as I will switch only when there is some relevant conversation or topic happening.
Telegram is LESS secure than WhatsApp.
https://www.wired.com/story/telegram-encryption-whatsapp-set...
... and Telegram FOSS [1] fixes all of the mentioned points?