Are we talking about for defensive shooting or competitive?
There are no guarantees and there are advantages and disadvantages to each method. I have missed as many or more slingshots and over the tops, than slide releases.
We talk about fine motor skills going away and all that, but we seem to be fully confident that we can hit the mag release button to initiate a reload, but we will not be able to locate and operate the slide release (I know, actually slide lock, but we're using it to release the slide in this context.).
The over the top - I learned this at Gunsite and it is powerful. Used it for many years and went to Blackwater. My instructor there related an incident where a guy used the over the top to clear a mal and it so happened the case was caught between the slide and the barrel WITH THE OPEN MOUTH OF THE CASE FORWARD!!! The guy did the sweep and the case ripped a swath of flesh all the way across the palm of his hand. . As the instructor put it, "He wasn't worth a **** the rest of the week."
Slingshot - not as strong as the over the top but good enough. The hand doesn't pass over a casing or the ejection port in the process so no danger of a case slicing a hand or the hand blocking the ejection port.
Mag release - pretty fast, lot's of top competitors use this method.
I now use the sling shot for two reasons, one because of what happened to the guy at Blackwater, two, because it is the same action you'd use in a malfunction drill. It's not that the slide release isn't a good way, it's that every time I use the slide release method, I miss an opportunity to train with the sling shot.