Below image from the chiselspeed site comparing them seems to indicate the ads is as good if not better?

"Above a Taffspeed Mk 4 was put to the test against the Chiselspeed ADS 3, Both of these exhausts are made for the same purpose, for use as a touring exhaust. The ADS 3 produces slightly more power with max horsepower standing at 21.90hp compared to the Taffspeeds 21.20hp. A very nice increase in torque is also achieved, The ADS 3 produces 19.53 ft-lb of torque, compared to the Taffspeeds 17.90, giving an increase of 1.63 ft-lb of toque over what was before spoke about as "the" exhaust to have as a good touring pipe"