Which Pokemon is stronger?

Question

Which is stronger a 252 adamant mega mawile or a 252 adamant mega banette. The attack is sucker punch and is neutral

The target is 252 hp Pokemon (no specific Pokemon)
Please tell me which one is better thank you

Answer 1

Okay so you want to see which is stronger;

An Adamant Nature, 252 Attack, Mega Mawile's Sucker Punch; or

An Adamant Nature, 252 Attack, Mega Banette's Sucker Punch.

Both with 31 IV's in Attack?

Well Mega Mawile's Base Attack is 105.
With 31 IV's in Attack, 252 EV's invested in Attack and an Attack increasing Nature (in this case Adamant), it's maximum Attack Stat is 339.
Then of course it has Huge Power which would double it's Attack Stat to 678!

Mega Banette's Base Attack Stat is 165!
With 31 IV's in Attack, 252 EV's invested in Attack and an Attack increasing Nature (in this case Adamant), it's maximum Attack Stat is 471.

The clear winner is obvious here but I've decided to do some damage calculations using a Pokémon that is Neutral (1x Super Effective) to Dark... Snorlax.

Also neither gets STAB since neither are Dark type.

Mega Mawile:

>252+ Atk Huge Power Mega Mawile Sucker Punch vs. 252 HP / 0 Def Snorlax: 234-276 (44.6 - 52.6%) -- 23.4% chance to 2HKO
(234, 237, 240, 242, 245, 248, 251, 253, 256, 259, 262, 264, 267, 270, 273, 276)

Mega Banette:

>252+ Atk Mega Banette Sucker Punch vs. 252 HP / 0 Def Snorlax: 163-192 (31.1 - 36.6%) -- 68.5% chance to 3HKO
(163, 165, 167, 168, 170, 172, 174, 176, 178, 180, 182, 184, 186, 188, 190, 192)

TL;DR:

Mega Mawile.

Answer 2

Mega Mawile's Sucker Punch would be more powerful thanks to its Huge Power ability - its Attack should be 339 (or something close, depending on its IVs) out of battle, but since Huge Power doubles its Attack in battle, it will actually act as if it were 678. Mega Banette would have an Attack of 471 (or something close) outside of battle, but since it does not have Huge Power, it does not get the doubling that Mega Mawile does.

However, this is the damage of one single attack we're comparing - it doesn't automatically mean Mega Mawile is stronger in general, just that it can deal more damage with a physical move. Lots of other things enter into how useful a Pokémon is - typing, movepool, ability to use certain strategies, etc. And if Mega Mawile were to lose its Huge Power ability, Mega Banette's Attack would actually be higher.