SSP can have an edge and DAP in the soil is

SSP is the most popular phosphatic fertilizer after DAP and it contains 3 major plant nutrients namely Phosphorus, Sulphur and Calcium along with traces of many micro-nutrients.
DAP is Diammonium phosphate, it is a series of water-soluble ammonium phosphate salts that can be produced when ammonia reacts with phosphoric acid.
SSP can have an edge in supplying Sulphur as it provides Sulphur also as a nutrient whereas DAP does not provide Sulphur to the soil thus it makes soil deficient in Sulphur.