[jhasse]

Telegram has an open specification, called MTProto. I guess XMPP wasn't good enough, so they DID develop something "better" (better for this specific use case).

Also federated services have their disadvantages, so I wouldn't necessarily say that's better.

[kh_hk]

The only disadvantages I can see on a federated service are security and the cost of running it.

Compared to the benefit of not restricting one-self to a platform, I would say federated is better.

[jhasse]

It's also technically more challenging.