One point missed is WhatsApp data is pushed to Facebook.. more oil for the Zuckerberg empire to get more cash off your details.
You cant tell me that whatsapp has any security when Facebook is in the picture. Security from maybe other people trying to intercept, but I doubt there is any security when uncle CIA comes knocking on their door asking for your chat logs.
Metadata, not data. They can't see the contents of your messages, but they can see who you're messaging and how frequently.
This complaint about WhatsApp being linked to Facebook is really amazing to me, because the donkeys that hee-haw about Telegram haven't looked past their noses. They don't realise that Telegram was founded by this guy:
https://en.wikipedia.org/wiki/Pavel_Durov
whose other big thing is VKontakte, which is basically the Russian version of Facebook.
Personally? I trust Zuckerberg *slightly* more than I trust Durov. Granted that's not much.
If I were an idealist I would use Signal, but now that Open Whisper Systems has done the end-to-end encryption for WhatsApp, and basically everyone uses WhatsApp while no-one knows what Signal is, WhatsApp is the way to go. (A messaging app isn't too great if you're the only one who uses it.)
It does P2P indeed as advertised. In consequence both peers must have Internet access in the same time, even for few seconds. Otherwise you will see a one tick next to the message instead of two.
Client-server architecture is more flexible and when I want true encrypted P2P for some reason, I will use secret chats in Telegram.
WhatsApp is totally client-server. Not P2P at all.
Try this experiment. Get your friend to switch his phone off, and send him a WhatsApp message. You'll get one tick-mark.
Then switch your phone off, and switch his on. Lo and behold! It will be delivered. The single tick-mark means that your message has been stored on the server for delivery but that his phone hasn't been reached yet. When you switch your phone back on you'll see both tick-marks.
Don't know what made you think it was anything otherwise.