So, I’m playing in a Pathfinder game again. (Yeah, I know; just when I thought I was out, they pull me back in.) It’s simple math, but I’m surprised there’s no core chart for the progression of Pathfinder’s Power Attack feat, which is only really a problem because I’m lazy and have a character who’s using it.
One of the big changes from 3.5 to 3.Pathfinder was how the staple Power Attack feat worked. Instead of subtracting -1 to -5 from your attack roll and adding a corresponding +1 to +5 to damage, Pathfinder streamlined the feat to give you a -1 attack penalty in exchange for +2 damage, which increases by -1 and +2 every time your Base Attack Bonus (or BAB) increases to a multiple of four. Ergo:
|BAB||Attack Penalty||One-Handed Damage Bonus||Two-Handed Damage Bonus|
Power Attack is one of those feats that people either love or hate. It’s a core requirement for most any Combat feat, so a lot of characters end up with it, but I’ve seen enough “Is PA Worth It?” posts to know it’s not everyone’s cup of tea (especially since it does nothing for characters who can’t hit the broad side of a barn). With a two-handed weapon, the damage bonus is sick, though it’s not doubled like it was in 3.5. With a single-handed weapon—if you’re going sword-and-board fighter—the damage is a good boost, but it’s not the end-all, be-all. Again, since you probably took it as a feat tax to get Cleave or something more interesting, there’s no reason not to make use of it when possible.
For the most part, choosing when to power attack is situational but based on standard logic. If you’re adding plenty of bonuses to your attack roll, or if the target’s fairly squishy (e.g., lower AC), there’s no reason not make Power Attacks. If the target is armored like a tank or otherwise hard to hit, you’re better off not bothering since the possibility for more damage isn’t worth the higher chance of missing.
For classes with fast attack progression (fighters, paladins, barbarians) who plan on wading into mêlée, it’s a natural fit. Of the classes with medium attack progression, the main beneficiaries would be combat-spec’d inquisitor or magus, and even then, they have other things to focus on.