I've used them both, side by side, and really don't see any difference in "separation". There is, however, a difference in how they respond to specific targets and the "smoothness" of the audio tone that specific targets produce. As with the other coils, the higher frequency is a bit more sensitive to lower conductive targets. And the lower frequency is a bit more sensitive to higher conductive targets. In my opinion, if the buttons you are looking for have a higher conductivity than the nails in the area (which I would assume they do), then the MF will "hit" the buttons harder. On the other hand, the HF should hit the nails harder. In other words, nails will make a more solid tone using the HF coil, compared to the MF coil. Even with some of the ferrous targets rejected. I know that it might not make sense to use a coil that makes a more solid tone on nails. But some guys hunt by audio differences (like I do with the 3 kHz concentric) opposed to rejecting certain notches. Recognizing the audio differences between the buttons and nails might be what he is going by? And the higher freq is definitely going to be more sensitive to the more ferrous targets, such as nails. JMHO. HH Randy