This comparison is as old as time. They are both used to exfoliate dead skin cells on the skin but they work differently on the body. Sugar is mild on the skin which makes it suitable for dry skin, sensitive skin, normal skin, combinations skin and mature skin. Due to its mildness on the skin it locks in moisture on the skin leaving the skin soft and smooth.
Salt is very sharp / harsh on the skin which ends up leaving the skin dry which makes it suitable for oily skin, its harsh property leaves the skin red so its best to exfoliate at night when using salt so the redness would have calmed a bit all through the night. Salt scrub is used for skin treatment like body spot. Add yoko salt with santarde leg cleanser and apply on the affected area frequently, it will gradually fade off the body spot leaving the skin discoloration free.
Though they both exfoliate the skin but sugar only ends in up in cleansing the skin which leaves the skin moist and soft while salt on the hand not only does it cleanses the skin but it also detoxifies the body.
Sugar scrub and salt scrub are both not advised to be used on the face. Its best to use an emulsion scrub as a facial scrub because it does not cause abrasion on the face. They are both not meant to be used on a broken skin