>>54141829Now look at the whole picture.
Mega Metagross can outspeed all base 100s, Kartana, Justice trio, Infernape, Blacephalon, and Garchomp, then speed ties Lati twins, Gengar, Mega Diance, and Mega Gallade. Metagross otherwise gets revenge killed easily by these Pokemon and likes of Gliscor, Landorus-T, Kommo-o, Gyarados, even Hoopa-U and Chandelure.
Also even with Jolly, the damage you get from Tough Claws is just about the same as what you’d get from LO Metagross (which if you do use LO, that just means you take 1/10th of your HP every turn).
Also also the bulk you get from Mega Metagross is in conjunction with speed. That speed means it can often avoid stronger attacks like ones from Moltres or Hydreigon because it knocks them out before they do damage. Meanwhile faster Pokemon don’t do much damage anyways. And if you were using LO like before, you’d have less HP to work with each turn. Regular Metagross has to leverage its bulk more often since it’s slower and will take more hits.