In the standard mode you simply race to complete the puzzle the fastest. In SudoKompete mode, you accumulate points based on the tiles which are connected to your newly placed tile both horizontally and vertically.
Placing a 1 in a position which completes both a horizontal row and a vertical column will provide the maximum number of point for a single turn. The newly placed tile is only counted once: 1+2+2+3+3+4+4+5+5+6+6+7+7+8+8+9+9=89. When you place a tile over an existing tile, the value of the tiles it is connected to is subtracted from the score of the player that placed that tile. Therefore it will negatively affect your final score when you place incorrect tiles on the Sudoku board.