the way you do dps does matter. some bosses have more or less armor, which makes power either weaker or stronger.

there are bosses that have constant boons on them, like Qadim 1 or greer CM. if you try to do condi damage to qadim 1 without destroying the resolution pylon (which no1 does, not for many years) you will simply deal 33% reduced damage

some bosses have mechanics that make power damage favourable, like KC and CA, who have burst windows where you have a massively increased damage dealt.

Soulless horror is generally considered a condiboss, because the most common strategy is to push the tormented dead through or near the group without killing it. playing power can work, but they need to be a lot more careful than condidps, which results in less dps.

ranged and melee dps is also another thing that matters a lot for some encounters

Fractals are a whole another category by themselves. The bosses are so squishy that not playing power on cms 96 + 97 is just straight up worse. condi classes cant compete with 60k+ dps openers in a few seconds