What IDX said and the same goes for me during gold prospecting or relic hunting in dirt that is too mineralized for the 11" coil. The 6" coil will not see as much of the hot dirt when close to the ground just due to it's size (similar to the EMI IDX mentioned). So it will operate much more quietly, ground balances quickly and good targets are easy to hear. Even at sensitivity settings of 15 to 20 it will get depth on coin sized objects deeper than its physical diameter. So, it punches way bigger than its size IF the operator doesn't overload it by turning up the sensitivity too high. Don't get greedy with the 6" coil. It was not built or intended to be used maxed out for depth. I do sometimes run it as hot as possible when I am finishing up an area that has produced really small sized gold nuggets that are really little like smaller than 0.1 grams. Otherwise, it will unmask larger targets much better at lower sensitivity levels.
Jeff