>>22141755But then he can't use an item. Pretty Sure Deoxys Attack does more when he uses a Life Orb. Also, Deoxys Attack has a better movepool (Hazards, can go mixed without much trouble, Extremespeed, Psycho Boost) and if speed is really getting you down, you can run Choice Scarf. Not ideal, but you can.
Mewtwo gets marginally better abilities, though. Unnerve, Insomnia, and whatever the physical mega's ability are all better than Pressure, which is only any good on Deoxys Defense.
