I think they’re largely equivalent. Appetite suppression and extra energy in the face of a brutal diet were the desired effects and both forms delivered in a satisfactory manner. The “fat burning” effect was negligible IMO
My understanding is that Ephedrine Sulfate is somewhat slower acting because Sulfate ion, also the HCL form has a little pure Ephedrine by weight, but in reality you're only really talking about +/- a few mg either way, so take what's handy.
The big problem now, speaking to a pharmacist I know is that both types are considered old fashioned and too cheap treatment wise so they don't get much shelf space anymore, and when it does it goes to areas where the population skews older.