I've never used RabbitMQ, but NATS supports clustering, super clustering, and leaf node connections. I'm guessing the latter is the closest to what would be considered "federation" in this context.
None of them are close. RabbitMQ has traffic shaping, MQ->MQ routing (federation), and all sorts of stuff that is super important if you use it as a generalized routing system (vs plain IP). NATS doesn't have that and it's almost certainly firmly out of scope.
When you say "MQ->MQ routing (federation)" I have a hard time understanding how that is not close to leaf nodes. Leaf nodes allow independently operated / managed NATS servers to share data back and forth, which to me is what federation is about. Do you have any resources you recommend to help me grasp why this is different?
Oh cool, I didn't know it could! Regardless, advanced routing is still something that RabbitMQ has that isn't in NATS. It's not useful for every system, but it is a differentiator. I usually reach for NATS + Jetstream these days, with its object and KV systems it's a really great "all-in-one" for basic stuff.
Edit: spelling