I say PU to pE.
As to the speed increases noted by Neblette, I think that he is rather conservative in his figures. Also, he has not included the very great gain in contrast afforded by sulfur. Sulfur alone can change an emulsion from a grade zero contact paper to a grade 2 enlarging paper with several stops in speed.
Finish formulas (sulfur + gold) are often as complex or more so than emulsion making formulas. I give "dump and stir" emulsion formulas and "dump, stir and heat" finish formulas, but the real world goes far beyond that!