Not going to give you any specifics, but will give you a few general impressions. Each demon is much more situational now meaning there are ideal fights for each demon, but fights in which the wrong demon will get you killed as well. Additionally each demon is looking for something different to appease it and a few will attack certain targets on site (in addition to what they did before). Challegha and Morossa I thought had the biggest drawbacks, though Challegha was probably my favorite demon overall when it wasnt killing me or my group. Mors-Gravis seemed to have the least drawbacks, but I never figured out what it wanted, which was a drawback for me. Harmentia was fierce, as long as I could keep one alive. Overall, old demons were easier to use, but these kept you on your toes more, or ate you (they usually ate me.)