Okay. What makes you say Atk/def over Atk/hp?
Welp, both works tbh, just training def evs will provide 2-3% low damage from physical attacks.
Ex: Machamp 252atk/adamant Dynamic punch will deal 50-59% damage to a 252def/atk ev Scizor
Atk/hp will be better i guess, cuz hp will provide low damage to both spatk/atk based damage done to scizor, but will take 2-3% more damage from a def ev sciz.
Ex: Machamp 252atk/adamant Dynamic punch will deal 53-62% damage to a 252hp/atk ev Scizor