Kimimaro High-Difficulty
Reason as to why I think this is because Curse Mark gives Kimimaro more stamina and I am not too sure how well the panther technique will fare against the bones. It really comes down to who tires out quicker. Both opponents are poised to strike at any moment when their target gives up. They both have fast, offensive attacks that are close-mid range. It's a tough decision, but I think in the end it is really the curse mark that gives Kimimaro an edge. Also, Darui seems to fare better in team matches rather than solo 1v1s, but that is just my take on it.