Higher than normal stats give you bonuses on quite a few things.
STRENGHT: Your bonus of Strenght is added to your melee attack and damge rolls.
DEXTERITY: Your Dexterity bonus is added to your AC and your ranged attack and damage rolls.
CONSTITUTION: Your Constitution bonus is added to your HP at each level.
INTELLIGENCE: Your Intelligence bonus gives you bonus spells.
WISDOM: Your Wisdom bonus is multiplied by 10 and is added to your EXP income at the end of a mission or combat.
CHARISMA: Your Charisma bonus is multiplied by 10 and is added to your Gold income at the end of a mission.