Hi Juha,
I would say the primary benefit for presence specifically, is that remote watchers are notified immediately - it does depend on the event type, I guess, as to just how important this is, but it can make a real difference in certain applications.
Secondary benefits vary by use case but may include things like simplifying the stack and/or removing single points of failure, or allowing for horizontal scaling up/down on demand - all of which are benefits of dmq overall.
Why do you ask?
Cheers,
Charles