it really depends on what you're fighting, I'm of the mind a fighter, since they have a zillion feats, should have precisions because situationally it's more DPS than power attack.
I'm not sure how you calc the to-hits these days . . . it almost feels like its all random as I posted recently a picture of a +88 grazing the green dragon in EE DDTW . . . but back in the day of D20 if you missed AT ALL you did more DPS with PA off. Not sure how that works now with grazes and the new Ghostbane'd to-hit mechanics.