/agree with LaRue.
It depends on who you are training, what their goals are and how they wish to implement it into their functional training.
I would personally argue that the less they do with more weight would be the best way to go. Most people fall into the “abdominal workout” = more reps.
They are a muscle like any other part of the body and are a mix of type I and II mucles fibers. The best way to stimulate their growth would be aiming for 2-3 sets of 16 or less reps.