[cmarinas]

Not really. What I missed most in Telegram was "delivered to device" status. While they claim such information wouldn't tell which of the recipient's devices received the message, I see it more as laziness on their side. They could have aimed for "delivered to any/one device" or "delivered to the default device". I personally care about whether a message was delivered (and the recipient would eventually look at their phone) or the server is down, recipient doesn't have a data connection etc. and I can try different communication methods. A "read" status is nice but the people I usually talk to tend to reply anyway.

In terms of message storage (ignoring government requests here), Telegram servers need to store them so that they can be provided to different clients/devices. For WhatsApp, OTOH, there are primary communication devices (phones) with end-to-end encryption and secondary clients that connect to the primary device to access the messages (rather than getting them from WhatsApp's servers). End-to-end encryption is available on Telegram as well but AFAIK you lose the ability to use secondary clients.

[Aoyagi]

But...they do have a delivered status. I think it's "delivered to the servers" (probably doesn't work in "secret chats"), but it fulfils the same goal. Edit: It does work in secret chat as well

And yes, Telegram has an option (a default state actually) to store the messages on their servers, WhatsApp doesn't have that. Beyond "E2E should be on by default", I don't see how this point is for WhatsApp.

[cmarinas]

"delivered to server" is different from "delivered to device". Let's say my friend is abroad with no roaming, I have no idea whether a message was delivered to him/her or not. WhatsApp has both.

As I wrote, I think (I might be wrong though) that if you enable E2E encryption on Telegram you can no longer use additional/desktop client.