That topic also showed the difference it mad with a 3 cent silver coin. With the threshold at the factory preset at 12, the coin gave NO signal, not even a peep. At a lower threshhold it gave a nice solid signal.
I prefer to keep the threshold low, but then you so not hear the null effect of iron. Due to this I like to hunt in all metal, yes, all metal. That way I hear the iron next to coins. Most places we hunt have been hunted for years by many people. Most clear signals from all directions are simply gone.
2 weeks ago I took my new x70 to a house that I have done in the past, twice. Once with an Garrett Grand Master Hunter CX, and with a Garrett 2500 GTI. The tones and the target seperation were awesome in all metal mode. I had one signal that gave a quick high tone and then a low tone with a normal swing. I probed where the high tone was, and pulled out a 1906 indian head. It was 2 inches from a bottlecap and 6 inches down, and had given it's own crisp signal. This was with the stock coil. I found 9 coins, but they were 3 wheaties and the indian. Not bad for a yard that has been pounded by me and many others.
In extremely trashy areas I sometimes can't stand the all metal mode, but normally this is the way to go. That way you know if there is junk next to a coin, and the depth is maximized.