Intelligence measures a character's memory, reasoning and learning ability, and is the prime requisite of the mage (and sorcerer). It will influence how many spells you can learn and what chance you have of learning new spells.
Wisdom measures a characters enlightenment, judgment and common sense. It is the prime requisite of priests (clerics and druids). A high wisdom will also give you saving throw bonuses.
So to answer your question, which one is better will depend on what character you are playing. If you're playing a cleric/mage, then they would both be important.
And Aurican is correct - the sorcerer is a unique class - you can't multi or dual with it.