I can't speak for others but I've been having tremendous success with the 15" on mine. On beach wet sand and in the dirt. In wet sand it's insanely deep. On land I've been running mine in Park 1 and 2, 5 tone adjusted to my liking, Iron bias 0, reactivity dialed back to 3, and sensitivity cranked up as high as it will go before getting chattery. In my opinion if you're swinging the 15" then you're looking for max depth over separation and reactivity 6 would be counter productive to what you're trying to achieve really. Every notch of reactivity you go up is about another 3/4" of depth loss or something like that I believe. Reactivity of 3 is still really good separation and you get great depth, on the beach I actually crank it down to 2. I uploaded videos to my YouTube a few days ago of the 15" pulling gold rings at 18-20" in wet sand and I have more footage I haven't edited yet on land finding silver dimes in pounded out areas. One of them was down about a Garrett pointer length plus 3-4", probably around 13" or so. Some of them next to junk and it still picked them out fine.