To me the size matters of the device. My norinco has an extended slide stop/release device that is easily manipulated with the strong hand thumb, therefore I use it and refer to it as a slide release. BUT, on my S&W E-series it is smaller and only comfortably operated with the support hand, since it is smaller. So I use and refer to it as a slide stop.
Personally I think the sling shot method is lame and slower. The argument of "gross vs fine motor skill"is pointless because pulling the trigger is a "fine motor skill" and if you can handle that, you can handle operating a slide release under pressure. That being said, I instinctively use the silly slingshot method on my S&W since the slide release is not functional for me.
So what you're saying is size really does matter.