Mirrored from Sudopedia, the Free Sudoku Reference Guide
Because the diagonals significantly reduce the number of Unavoidable Sets, the puzzle can contain less givens than a standard Sudoku. Also, the diagonals create opportunities for additional techniques, such as Skewed Fish (Triangular Connection, Crossover, Double Crossover, Finned Double Crossover, Skewed Swordfish), Multiple Crossover, Weak Link Square and Skewed XY-Wing.
The diagonal constraints are also used in several other variants and sizes. For example, the Killer variant can be combined with diagonal constraints to form Killer-X. A more extreme example would be Clueless-Shaolin-X.