Gof overall, attack level: situational, though I would get more attack level on those attack daggers first.
Do you even play sin ? I know you do, but if you're really saying this, you suck at it.DPH sins should always use GoF, some times attack level, but GoF is overall better.
Id say better use +20 Atk daggers instead of other ones. I dont really like GoF because you sacrifice hp, even if you got BP, but yeah, Id say overall +20 Atk is better.