Since I never really used Fightceus that much, I had nothing to go on. Therefore I used the main sets in the calcs. Idk about the other guy but I don't know if he is using your spreads either. ChuckHades actually used a defense boosting nature in his calc, as a matter of fact, therfore he can't pull of the same amount of damage as you build does. Ofc I have no real answer for your argument Go10, since as I said (and you said) I am kinda deadbrained when it comes to this poke.
ChuckHades, I never assume Life orb on E-killer, IMO it is a bad item on it.
+2 252+ Atk Silk Scarf Arceus-Normal ExtremeSpeed vs. 252 HP / 176+ Def Lugia: 205-243 (49.27 - 58.41%) -- 64.45% chance to 2HKO
About which poke is worse against Mewtwo isn't really relevant actually. All that really matters is that Fightceus is in way more trouble since it gets one shotted by its STAB. And I wasn't talking about CM fightceus that much either, more like something similar to your set, the utility counter set (which apperently isn't a good set for checking E-killer, as Go10 told me in his post).