A golf ball having a thermosetting polyurethane cover composed of a blend of polyurethane prepolymers is disclosed herein. The blend may be a dual blend with a TDI-based polyurethane prepolymer blended with a second diisocyanate polyurethane prepolymer, typically a PPDI-based polyurethane prepolymer. The blend may also be a tri-blend with a TDI-based polyurethane prepolymer blended with two other diisocyanate polyurethane prepolymers, typically two different PPDI-based polyurethane prepolymers. The golf ball has a durability of at least 3.5 on a shear test rating of the cover.