In terms of income or in terms of daily stress?
Some would argue that orthodontists have less stressful days since they don't do much of the work and delegate everything. However, having a ton of kids and teenagers run around all day long would stress me out. I would much rather be staring the orifices of canals all day, seeing less than 10 patients a day. Not to mention endodontists have just about the lowest overhead of any specialty. Low overhead, small staff size in the office, few patients = low stress.