Telegram is by far the best messaging app. And the native apps for desktop (without the need to be connected to an active device) an device make it a fantastic app. It's fast. Sending images on iMessage is a 3 touch process and then actually sending is awfully slow. I have converted my social circle and family to Telegram and no looking back.
I always say, use what is best for you, but most people who move over don't regret it.
Also, it isn't Facebook. That is reason enough.
I got immediately repulsed with WhatsApp the moment it was taken over by Facebook. I knew this is just to gain more hooks into our lives with contact info and such and I am never happy with this. At the very least, if this guy wants to know everything about the world, he better have a live cam streaming the minutiae of all aspects of his life to the world. Surely, the guy who wants to rape the privacy of the world and is successful at it, shouldn't mind if his own privacy is up for grabs by the world.
However, more depressing is that people are happy he is raping their privacy. They will question those who raise their voices against the raping of their privacy.