I too was trying to decide between the two, and don't remember exactly any more why, but the scales were tipped in favor of Dr. Clark zapper. I ordered the one from Canada and used it a few times and felt better afterwards. Don't know if it was a placebo effect or not; unfortuantely I don't have the time to use it regularly, but am planning to use it again. I found that at least in my case some other remedies bring almost instant change for the better, and zapper was kinda so and so. Whatever I have is damn stubborn and agressive and zapper seemed to weak for it, but I was not using it regularly either.