Hi Arun,
I'm the product manager for BigBlueButton.
Jitsi and BigBlueButton are two open source conferencing systems. Jitsi is very strong on video conferencing and, over time has added more collaborative components, such as raise hand. BigBlueButton is focused on on-line learning and on enabling the presenter to collaborate with users. As such, we put a lot of emphasis on interaction and engagement (such as multi-user whiteboard and breakout rooms).
We have been moving BigBlueButton from a Flash-based client to HTML5 client. Jitsi is pure HTML5. For video, Jitsi uses Jitsi video bridge whereas BigBlueButton uses Kurento. Both Jitsi video bridge and Kurento are selective forwarding units (SFU), which means they pass through the video packets. This is similar to how red5 works for the Flash clients.
We're very impressed with Jitsi and their video capabilities. We aspire to do as well as they do in video conferencing:-).
Both are platforms are open source on which others can build their own collaborative capabilities. Both are under active development. We recommend that anyone interested to check out both platforms and see which one best meets their needs.
Regards,... Fred