I am exploring possibility of implementing distrubited Pub/Sub. I came across distributed Pub/Sub Event System and StreamInsight. What are pros/cons of both and under which scenario it should be used...

Thanks

The pub/sub system is transport for events. It gets events from the publishers to the subscribers regardless of where the subscribers are.

StreamInsight is a complex event processing engine. StreamInsight doesn't transport events so the pub/sub system and StreamInsight fit together quite nicely.