There have been a few reports of experiencing more power on the 24v setting.
I confirmed Monkey Magic's claim a while back when we were experimenting with the old internal controllers.
I cant say its the same for the new controllers, but I do believe the PWM is shifted when you change the program voltage settings, it must be to accommodate for the controller shunt resistance at the various voltage settings, in order to keep the current setting more accurate across all voltage selections.