I shoot on an indoor range , cast lead bullets with lithium-beeswax lubricant. I don't notice any difference in the two when shooting 38 special and mid range loads.
Maybe I'm not as bothered by a little gun smoke , my first revolver was a replica 1851 Navy cap and ball, compared to black powder , both are smokeless . Both will burn clean if loaded to their required pressure, light loading both will develops a low pressure and incomplete burn that most translate as a "dirty " burning powder.

Universal was developed to get some of Unique's big market...I've tried it and prefer Unique . Don't light load it and it will burn clean.
Gary