One small argument in favor of the universal overhand technique is there is no reason to assume that the gun you will use in a fight will always be yours.
Steve, thanks for the great post. It's a challenge for a newbie to sort out the different ways of doing things. As my wife and I continue to take training we'll continue to find instructors who have their own way of doing things. The LEO instructors for my one day tactical pistol class emphasized over-hand, but I have no doubt in a full-week of law enforcement training they would have discussed and taught the other techniques. And the slingshot is using our wonderful opposing thumb which over man's development has proven pretty darn reliable.I'm a LEO firearms instructor and teach all three methods; over-hand, slingshot and slide release. In fact, I had this conversation with one of my officers last night.
Learn all three, use what works for you. But know how to do all three!! If all you learn/use is the over-hand, what are you going to do if one of your hands is injured? Ask a new shooter to rack the slide and most will use the slingshot. Why? Because it's a natural movement.
I also do not believe in the loss of "fine motor skills". Anything with your hands; racking the slide (any method), reloading, opening a door is a fine motor skill. If a shooter is expected to be able to hit a teeny, tiny magazine release, insert a magazine into a magazine well, press the trigger, then why in heaven's name can they not be expected to hit the slide release???
I go with the overhand method because it is easy and I can do it with semi-numb hands (practicing in Colorado winters forced some changes). I figure if I can do it with numb fingers, I can probably do it under some stress.
In fact, attempting to over-hand the M9 brings it's own problem...the risk of inadvertently placing the gun on safe.
I carried a Beretta 96 on patrol. My "tap/rack" method was "tap, rack, safety" in which I physically made sure the manual safety was disengaged as part of my immediate action.