I hear man people talk of how clean 231 is. I just don't experience that in my testing with it. I have shot light 38s, full throttle 38s, light 45s and max effort 45acps with it and it was dirtier than AA#2 or 700x in every single test.
WST does burn cleaner than W-231. However, as a reloader for almost 50 years I am puzzled by the continued emphasis on the burning characteristics of powder rather than the end result - accuracy.
My favorite 45ACP accuracy load is 3.8 gr. HS-700X behind the 185 gr. LSWC for ca. 710 fps - a very mild and accurate load at 25 yards. It spits out grains of unburned powder grains but produces consistent velocity spreads of less than 10 fps. By current standards it would be considered a dirty burning powder but I love the end result.