I'm not very well acquainted with how bridge specifically built on top of rabbit, but I do use rabbitmq for other systems and in general, rabbitmq is more of an "enterprise" message broker and covers more bases for you than zeromq, while zeromq leaves more open to the developer to implement themselves. The most critical specific example of this used to be message durability & HA, not sure if that's still the case as I haven't looked closely at zeromq in a while. ZeroMQ was slightly better for low-latency, high throughput systems where losing a few messages was okay... Whereas rabbitmq was preferable if you needed to make sure you don't lose any messages. Of course, you can probably achieve the same goals with both systems, some things are just easier in one or another.
Thought I'd chime in as your message addresses general messages queues in addition to bridge. I would be interested to hear the bridge developers' commentary as well.
-Alex R.
CTO | Enplug, Inc.