Mechanical hackamores (like a Little S) have shanks, so can have extreme amounts of nose and poll pressure. (10× what your hands apply) I don't ever use a mechanical hack on any horse. A Side Pull is a nice alternative to a snaffle bit, for a horse that does not ride nicely in a bit. Side Pulls work as: Right hand pulls horse's nose right, left hand pulls horse's nose left. I can put a side pull on any horse I have and control them the same as with a bit. Bosal or Dr. Cook bitless bridles work fairly similarly. They work well for a horse who neck reins or is learning to neck rein. All so for a horse who just doesn't like bit pressure. Touching with both reins gives a pressure on the nose to encourage rounding. Touching with the left hand puts pressure on the right ride of the face, encouraging a turn to the left. Right hand - left face - turn right. My horse is a completely different horse when I ride him in a Bosal than his Waterford bit, he is more forward, less inclined to get "stuck" and less inclined to buck. This change is regardless of how much contact I have on my reins. I hope that helps!