A lot depends on the angle you are heading relative to the wind and how strong and variable the wind is and how easily you want to be able to steer or hold your course.

The simplest case that I think you might be wrong is going down wind, especially in light air, you want the sail to catch the wind like a bag and direct it toward a central point to add all the vague forces into one direction instead of just twisting the sail one way or another. Like I didn't think you actually want the wind hitting the outer edges of the sail straight on as this would just move the sail, not the boat.

Stiff, even hard not cloth sails are useful to go into the wind at a slight angle, where they are optimized in shape like an airplane wing, and they even talk of the force generated as lift.