Hunting in a true All metal mode you will often/usually/possibly get an audible hit on a near-pass target. One that is just a little too far from the coil for it to respond when in the Discriminate mode, and it's possible that a return sweep in that mode will be farther off. By hunting open areas in All Metal (a conventional Threshold-based All Metal), you increase the odds of hearing a target on the fringe of your coil during the sweep and can redirect the sweep to better acquire the target and check it in the Disc. mode. It also lets you know if the site is target-free, or if there is some iron that can cause masking. I hunt in All Metal mode a bit over 50% of the time, depending upon the site I am hunting.
I agree with a couple of your other statements that the idea of changing to a toggle is often a "gee whiz, look what I have" attitude that gets done just to do it by some, but some modifications are functional.
The Vaquero does have the same pushbutton feature as the Cibola as well as a clicked setting for All Metal operation.
Monte