Is it better to have too much intake or too much exhaust ventilation?

It is better to have too much intake airflow than exhaust airflow.

Ideally, the attic ventilation system would be evenly split 50%/50% intake and exhaust. That is the primary goal. If the system is going to be out of balance try to always be out of balance with more intake than exhaust because the excess intake vents will act as exhaust vents on the leeward side of the house.