One of the largest benefits to having a bridle handmade is that it will be almost entirely stitched by hand. This means the threads actually pass through the leather from the front to the back and vice-versa at every stitch. If one stitch is worn away, the rest do not loosen but continue to hold until they themselves are worn away. This means hand stitching last much longer than machine stitching.
When a machine stitches, it is only looping the top thread through the bottom thread at each stitch, meaning when one wears or loosens, the stitches either side will loosen too. A stitch in time saves nine is certainly applicable in the case of machine stitches. Machine stitches are naturally slightly looser to begin with than hand stitching.
Visually, a machine often marks the leather on the back, front or both depending on how it feeds the item through. This is a good test to see if an item has been machined or stitched by hand. There should be no marks at all if stitched by hand. Another visual test is the angle of each stitch because most machines will barely show any angle at all in their stitches, whereas hand stitching each stitch should be angled the same way by the same amount.
Machine stitching is only used on IR Bridles for rubber grips on reins because this allows easier replacement of the rubber in the future and the rubber will most certainly wear out before the stitching does.