I use iMessage primarily, it has end-to-end encryption and your messages are stored in iCloud. It also integrates wonderfully well with your Mac.

I'm still logged into WhatsApp though, to keep in touch with the ones using Android, but I've switched notifications off so I just go into check as if I'm checking my email.

I wanted to check out Telegram as a WhatsApp replacement but very few people seems to be using it.