I always question authority - I want to know why they recommend what they recommend. In some instances someone will adopt a technique and since they are subject to the same ego and pride as any other human, recommend their way as the best and then find rationalizations to back it up. OR - perhaps they are used to training non-gun enthusiasts who aren't going to really practice much so they need a one size fits all approach.
It's like the guy who told me X brand trucks suck, never ever ever buy an X brand truck - and he should know since he was an expert in brands X, Y Z and a few others. So I asked him why, and his response was that they don't come in any color he liked. Point is, ask the reasoning behind someone's recommendation and then judge for yourself if that reason is something you can use. Maybe it is, maybe it isn't.
I'd say go with what suits you. For some 51 years now a semi-auto pistol to me meant a 1911 or a Ruger Mk of some kind. From age 16 when my Dad bought a Colt Gov't Model I learned to use my index finger to release the magazine and then to reach up and drop the slide with that same finger. Slingshotting a Ruger Mk pistol means pinching the ears with the thumb and second joint of the index finger, not reaching over the top. Same same with any pistol now, I use thumb and forefinger if I want to use that method at all. Up until this year my only other centerfire auto was a Beretta 92FS and I can operate that the exact same way as the 1911's I used for so long. Grabbing the whole slide on that really risks activating the decocker and safety, if my thumb and forefinger contact the decocker at all they are pulling up on it.
To me using the lever attached to the protusion that engages the slot in the slide is a faster method since I can be re-acquiring my grip simultaneously, second fastest is the slingshot with thumb and forefinger since the arm and hand have to travel less distance to re-acquire the grip. To someone else maybe a totally different way works best.
Now since the nice pistol manufacturers have begun putting a metal nub on the right hand side of their products, and allowing the magazine release button to be moved over as well, I've been practicing using my thumb to release the mag and drop the slide. The right side mag release is definitely nicer, as is the right side whatever you want to call it on a Glock G5 and a Sig P320. With a full magazine they disengage the slide easily and I'm ready to go. The S&W bugs me because I'd like to use that as well but the right side WYWTCI is practically useless.
There is a definite advantage in finding one method and then sticking with it, that's what caused me to sell or put away four pistols with different controls and different trigger actions and go with totally striker fired, ambidextrous pistols.
Fwiw, I did buy an X brand truck and it was a wonderfully reliable vehicle for the 13 years I owned it.
