I think it is very hard for anyone to answer this question. It depends on so many factors that I do not know where to start if your two basic questions are "How should I make the comparison? what are the features I have to look for? " I'd suggest you start reading in general about BPM first and than come back with some more detailed questions.
Ofcourse I have a personal opinon. I have worked with Bea WLS for the last few years in which they had 3 different BPM products. They are currently being mentioned as a victim (or the lucke one) of a possible take-over by Oracle, which had 3 BPM products in the last 7 years as well.
Continuity would be high on my list (besides opensource, support, flexibility....)
Our infrastructure application server is WebLogic 8,1 which I think eliminates any chance for AquaLogic BPM and I'm not sure that we going to update to a newer version.
So, Does jBPM works on WebLogic 8.1?
Yes it does
Where can I find an on line jBPM sample application that is ready to be deployed on WL8.1?
I think you will not be able to find that somewhere, online or offline.