One of the most common arguments for using the overhand method of releasing the slide on a semi-automatic pistol is that it’s a “gross motor skill”. I use to repeat this argument myself before I actually understood what a gross motor skill is:
Motor skills are actions that involve the movement of muscles in the body. They are divided into two groups: gross motor skills, which are the larger movements of arms, legs, feet, or the entire body (crawling, running, and jumping); and fine motor skills, which are smaller actions, such as grasping an object between the thumb and a finger…
The logic of the gross motor skill argument falls apart when you examine all the other actions involved in getting to the reload: aligning the sights (fine motor skill), pressing the trigger (fine motor skill), and pressing the magazine release to reload the gun (also a fine motor skill). According to the gross motor skill theory, even though I was successfully able to perform at least three fine motor skills, all of a sudden my brain is going to go on the fritz when I try to reload.
This doesn’t mean that there aren’t situations where training the overhand reload makes more sense – as someone pointed out in the comments, a lot of military and LEOs are issued and wear heavy gloves that can make manipulating the slide lock clumsy and difficult, those guys should definitely train for the overhand method. Similarly, if your chosen carry gun doesn’t reliably drop the slide when you use the slide stop, train for the overhand method. A really good example of this is the Ruger SR-series of pistols; Ruger specifically says in their manual to use the overhand method, since the slide-stop isn’t really designed to drop the slide.
I think there are some really good reasons to use the overhand slide release method, as mentioned above. But as a community, I really think we should disabuse ourselves of the notion that it’s a gross motor skill – gross motor skills are things like running, walking, jumping, or swinging a shovel into a zombie’s face. Pulling a trigger, ejecting a magazine, any both methods of releasing the slide are definitely fine motor skills. The nice thing about that is that fine motor skills can be improved with practice and repetition, so whichever method you decide is best for doing slide-lock reloads, make sure you spend time practicing it!