It depends on the rates used. Applied at rates that just cover a crop’s sulfur needs, neither one would do, regardless of the soil type. When thinking of these products as soil amendments, 200 to 400 pounds per acre of elemental sulfur, and double that amount of ammonium sulfate, would be needed.  It should also be noted that, unless it is in the powder form, elemental sulfur will take some time to oxidize, and that way acidify the soil. With ammonium sulfate, on the other hand, as soon as the conversion from ammonium to nitrate takes place, so does the acidification process.