Which of these chest mods is better? They both seem to fill the exact same role in a build, or am I just missing something.
On a straight 1-1 comparison, penetrating strikes is better. However, I don't know if anyone has tested them when defense debuffs are in place (especially now that there are several that can be stacked via allies and heartbreak). Now, considering that %-based buffs and debuffs are almost always additive as opposed to multiplicative, the answer most likely is still penetrating strikes. But I don't know if that has ever been confirmed via proper testing.
Defense debuff has no effect on penetrating strikes since enemies don't have that defense stat (shown in OC's test). They simply have a hidden modifier that reduces damage taken, depends on difficulty/mechanic and defense debuff doesn't remove that. In addition, there are like 3 brackets when it comes to damage like "Stat buff" (%might,prec,etc), "Damage buff" (+%damage,etc), "Defense debuff" . Penetrating Strikes isn't in any of these brackets so it's always that flat 2%, while Core Strength is in the "Damage buff" bracket, so additive with anything in that such as innate stat when in Damage Role (DPS).
I get what you're saying and there's a good chance you're spot on. But that modifier is an actual number which is reduced by defense debuffs. Penetrating Strikes "ignoring" 2% of that full number without being reduced by defense debuffs might be different than when it is ignoring 2% of that number after being reduced by defense debuffs.
That modifier (mechanic based) isn't affected by defense debuff, even if you don't see the green shield on enemy, it still exists, and it's also easy to check if you spam fear gas with and without defense buff, during specific phase for example. Also difficulty modifier applies right the moment you enter contents such as elite plus, again defense debuff has no impact and will not remove this modifier. You should see your damage cut by near half if you run those contents. As far as I know, there is nothing that affects penetrating strikes, it's always 2% regardless of enemy types, or whatever buffs/debuffs they have. The numbers might be different because of the base damage of abilities, it's not a fixed value for a majority of abilities in this game.
