The meaning depends on the context. According to Picken's "A Dictionary of Costume and Fashion" (and to a person studying fashion design), a "cuff" may be a "finish for sleeve or glove, for wrist or forearm" (p. 91), such as a single cuff or a double cuff. A "wristband" is "1. Band on a sleeve at the wrist. 2. Useful or ornamental band or bracelet worn on the wrist." (p. 382).
Usually when someone says "wristband," I think of a tennis wristband, which is absorbent, like what AldRin described above. After that, the word "wristband" might make me think of friendship bracelets or something like that.