Ephedrine Sulfate--MW=428.55, Ephedrine MW = 330.46 ----> ~77% Ephedrine
Ephedrine HCL--MW= 201.70, Ephedrine MW = 165.23 ----> ~82% Ephedrine
So now,
25mg @ 77% ~ 19.25mg Ephedrine
VS
12.5mg @ 82% ~ 10.25mg Ephedrine
Use this to see which is better for the money. If the products are similarly priced, Ephedrine Sulfate is the way to go.