Pull does have advantages over push (e.g. one-to-one flow control since the transfer of the messages is initiated by the client (pull requests)), and they are basically functionally equivalent (only thing push can do that pull can not is send a copy of all the message to all the subscribers, should you ever need it). They both exists because historically push came first and then pull later).
As a developper using NATS JetStream you should really not have to worry about push or pull, you should just care whether you want to consume the messages via call back or via an iterator or via fetching batches, after that whether pull or push is being used underneath the covers is irrelevant to you.
And this is exactly how it is in the new JetStream API (https://github.com/nats-io/nats.go/tree/main/jetstream#readm...) you don't have to worry about push/pull anymore and you can consume in any of the 3 ways described above (callback, iterator, fetch batch) it's all a lot simpler and easier to use.