They reported a main difference of clavicular head muscle activity between 100 % (superior) and 200 % grip width. (strengthandconditioningresearch.com)
But the closer grip also provides a major benefit for chest training, as it allows for a greater activation of the inner fibers of the sternal and clavicular portion of the pectoralis major. (fitnessandpower.com)
Glass & Armstrong (1997) compared the 15 degrees below horizontal decline bench press to the 30 degrees incline bench press and found no difference in pectoralis major clavicular head muscle activity. (strengthandconditioningresearch.com)