This:
"This means that staffs are far more potent in the hands of a powerful spellcaster. Because they use the wielder’s ability score to set the save DC for the spell, spells from a staff are often harder to resist than ones from other magic items, which use the minimum ability score required to cast the spell. Not only are aspects of the spell dependant on caster level (range, duration, and so on) potentially higher, but spells from a staff are harder to dispel and have a better chance of overcoming a target’s spell resistance."