Potential & Enhancement System Guide

From what I heard %attack doesn't affect attack coming from skills/potions so %total damage would be better. Though it shouldn't be too big of a difference except for apples.

% weapon attack is also unaffected by stars and bullets, so any classes gaining additional WATK from similar items don't get an additional boost from the potential bonus. In the end, % total damage is essentially always better as it slaps a nice multiplier on to the end of the damage formula for whatever skill you're using, and doesn't fluctuate when you lose or gain WATK/MATK, and of course still helps the same when using buff pots.

EDIT: So in my opinion, the best possible weapon stats for anyone looking to boss would be:

+9% Total Damage
+9% Total Damage
+30% Damage when attacking a boss

Note that additional bossing damage bonuses do not stack with one another, so with this kind of weapon giving an additional 1.48x multiplier at bosses, it's the best of the best.