Joram Barrez has a really interesting post about process performance with Activiti.? It doesn't compare the engine to other products- but it does compare different configurations of the product.? Its the kind of internal performance testing that is pretty interesting to get insight into, as an "outsider" to the company or development team.? Characteristics about how things like this perform can either confirm or contradict what you assume about the product architecture.
For one thing, it looks like it pretty efficiently uses more cores, and there are interesting database results:
The results speak for itself. Oracle blows away any of the (single-threaded) results on MySQL (and they are already very fast!). However, when going multi-threaded it is far worse than any of the MySQL results. My guess is that these are due to the limitations of the XE version: only one CPU is used, only 1 GB of RAM, etc. I would really like to run these test on a real Oracle-managed-by-a-real-DBA ? Feel free to contact me if you are interested!
I suspect he's right about the limitations of the XE version...