I can't speak to the Dr. Schulze cayenne tincture since I've never had it. I can say that I've had several bottles of cayenne tincture from Uny and they all taste the same to me except for the fact that I've gotten used to the "hot" burn.
The first time I took her tincture I did what I call the "cayenne happy dance" all around my kitchen but along about the 4th day or so it didn't burn nearly as bad and after months of using it its even less now. I think the fact that the hot feels less hot is in reality due to my taste buds having built up a tolerance for the "hot" taste.
Have you considered this possibility? Just my thoughts on the matter.