I believe the reason(s) for the variation(s) in Excalibur performance are far more complex:
Essentially this detector is a switch and potentiometer type of instrument which wears and deteriorates over time plus it built and repaired with discrete components whose bias will drift. That is the reason some detectors are hot in performance while others are not within the same model. The performance will also be affected by the skill and competence of the technician which assembled/repaired a given detector and if it is a variant of a factory model which has been customized for improved performance.
To summarize the above there is a variation in the performance of individual detectors as well a difference in performance between Excalibur Models/Variations.
Vlf detectors can detect incredibly deep targets. A silver cache was detected with a CTX 3030 at six feet, and I have detected and retrieved oversize targets with the Excel ll 1000 and Bounty Hunter Pioneer 505 at three feet. Since you don’t want to go there unless you know it is not trash. VLF detectors are usually calibrated to tone on a quarter size target ( most are coin shooters) say for example 6 to 8 inch on a mid level detector and 10 to 12 inch on a more expensive detector.
The difference in depth between pin point and discriminate is also beach specific depending on the mineralization, and conductivity of the soil which can change dramatically on some beaches, while others it is so slight that it is difficult to automatically ground balance. Further if there are iron objects close to the search and receive coils it may distort the magnetic field(s).
And like you said it is a matter of your hunting style and your skills such as overlapping, sweep speed, coil control, etc, etc.
IIRC, 27 variables have to be solved simultaneously to determine the location of a single target.
I think the variations in the Excal experience is largely a user difference. I use disc and PP both on a regular basis and I see very little difference in depth, maybe an inch or two at most depending on the target. As far as a learning curve, I think the changes in threshold along with the multiple tones tends to confuse a lot of people who aren't use to that sort of a thing, for them the learning curve is probably greater. One thing to remember about the Excal is that when hunting in disc the threshold can still shift over a target without presenting a tone, so even in disc it is still hunting deeper then a lot of hunters realize. Whenever I experience this shift in threshold while in disc I always switch to PP and rescan the area. This same thing can be said of nulls, especially when using the larger coil, if that threshold returns with a mid to high pitch then it may not be iron.
