Is it mainly down to preference, or are there any crucial KO breakpoints that Gallade would miss out on taking Psycho Cut over ZenButt? I know having the flinch chance is nice and M-Gallade has the speed to abuse the chances, but recently I just had the worst luck and missed four ZenButts in a row, and was just wondering if the increase in reliability could cause an inability with the drop in power.
That, and thematically I think Psycho Cut is infinitely cooler.
I suppose missing so many Zen Headbutts in a row is just some really bad luck, but I think that the higher power more than makes up for the higher accuracy Psycho Cut provides (
even though the latter even sounds better): not only it has roughly 14.50% more Base Power, but Gallade can actually abuse its nifty flinch chance and it doesn't miss as many KOs.
Here are a couple of calculations against some targets for our Psychic coverage:
Against MegaHeracross (not really the most relevant target, but just to show my point):
252 Atk Gallade Psycho Cut vs. 40 HP / 0 Def Mega Heracross: 242-288 (77.8 - 92.6%) -- guaranteed 2HKO (MegaHera lives the hit and OHKOes with Pin Missile);
252 Atk Gallade Zen Headbutt vs. 40 HP / 0 Def Mega Heracross: 278-330 (89.3 - 106.1%) -- 37.5% chance to OHKO(MegaHera is much less likely to live the hit, and Stealth Rock alone secures the KO);
Against a weakened Clefable (the Unaware variant):
252 Atk Gallade Psycho Cut vs. 252 HP / 252+ Def Clefable: 120-142 (30.4 - 36%) -- guaranteed 4HKO after Leftovers recovery
252 Atk Gallade Zen Headbutt vs. 252 HP / 252+ Def Clefable: 138-163 (35 - 41.3%) -- 75% chance to 3HKO after Leftovers recovery
(Psycho Cut has a chance to miss the KO against a <50% Clefable and allow it to regain health with Wish or hit you with Moonblast, while ZenH doesn't have as many issues)
These are the only calcs that spring out of my mind, but in the end I suppose it just comes down to whether one favors power against accuracy.
EDIT: Kinda ninja'd by silver97.