Hi Sanjay,
I must say that I am agree with Bernd. If you need support from red hat, you should choose jbpm3. There is no such support for jbpm4. jBPM5 does not start yet. And Activiti is still in alpha state.
If you choose to use jbpm4, it means that you won't get any official support from red hat. We have only community support, e.g. this forum. So if you have not start yet, please think about it carefully.
And I think jbpm3 is more stable than jbpm4, although jbpm4 is much easier to learn and use. I believe jbpm3 could satisfy all of your need.