In my experience, the Detech 13 is slightly less stable than the stock coil (I find myself occasionally lowering the sens), but if response is set to long, I have little trouble myself hearing coin-sized targets among the chatter, even at 30.
I usually just put the 13 on, crank to 26+, and do fine with it, but do put up with the noise. I'm hunting mostly hunted out parks and fields, and think the Detech 13 is a good choice for those sorts of sites.
And, as far as iron falsing, I think I've dug less iron that with the stock coil. Could be cause its been quite dry around here until recently, and could be site specific, as I tend to stay at the same site day after day rather than move around.
Unfortunately, since I only have one shaft, and changing coils is a hassle, I've been unable to do side by side tests against the stock coil, and that is really what you have to do at your sites to have a good answer, IMHO anyway.