What is the difference between pubSub(XEP-60) and push notifications(XEP-357) in XMPP in terms of the use-cases which they can or cannot support. From what I understand, in PubSub, the nodes(lets say the clients) can subscribe to a topic, and the publisher(lets say the XMPP server) and send messages to all the clients which have subscribed.
Isn't this functionally similar to push notifications? What is it that can be achieved using push notifications which can't be done using pubsub and vice-versa.