So before answering your questions.. my question to you is: what is a large project? how are you planning to use jBPM? which pieces of your application are you planning to use?
Its a little bit difficult to compare 3 with 5 for serveral reasons:
1) different modeling language
2) Different toolings (in 3 something like guvnor didn't exist) so you are comparing nothing with some big project
3) The business scenarios that can be solved with 5 are much more complex that the ones that you can solve with 3
Cheers