Why have DD coils become the standard coils on most newer detectors? Granted, the DD coil is better in bad ground and doesn't require as much overlap, there are a lot of advantages to the concentric coils. First off, pinpointing is typically easier, ID is better and depth is better for the equivalent size. If you're not consistently hunting bad ground, you would probably do better with a concentric coil. As for the overlap, my thinking is that you need to be overlapping anyway, even with a DD coil, since hitting areas from different angles can reveal targets that couldn't be separated out at the initial angle of attack. There are advantages to both coils, but if I'm not hunting bad ground, I really prefer an elliptical concentric.