This is not a battle between the two directly, but a fight where they control an army.
They are both given 100 healthy and newly trained soldiers and must command them to defeat the opposing army.
Lelouch is a tactical genius who can adapt to any situation in battle as a commander he also has his experience fighting against Brittania and his own Black Knights..
Iskander is a heroic spirit who holds the title of king of conquerors, and has A rank charisma which boosts the skill and morale of his soldiers, as well as his own leadership.
Battlefield is a flat plain.