In scotch tension setup, I can spin much faster. I can choose smaller whorls for the flyer and not be concerned about the bobbin whorl size. I can also setup the bobbin with any take up I want, doesn’t matter about the flyer whorl size.
I don’t find nothing wrong with consistency of the yarn I make in scotch tension. It works just as good for me as double drive.
I also do not find nothing wrong with the treadle in scotch tension versus double drive. As long as the tension is setup properly it treadles smooth. With proper setup the scotch tension can treadle nicer than double drive.