Power Attack:
On your action, before making attack rolls for a round, you may choose to subtract a number from all melee attack rolls and add the same number to all melee damage rolls. This number may not exceed your base attack bonus. The penalty on attacks and bonus on damage apply until your next turn.
Combact Expertise:
When you use the attack action or the full attack action in melee, you can take a penalty of as much as –5 on your attack roll and add the same number (+5 or less) as a dodge bonus to your Armor Class. This number may not exceed your base attack bonus. The changes to attack rolls and Armor Class last until your next action.
这里第一没有提指定，第二没有提free action；于是，我觉得可比性并不是很大... 不过，我现在倒是比较倾向DM的说法了，虽说规则上没有说不通的地方...
