If I take two Pikachu's with 0 IVs, and an equal Sp. Att. of 50, the base Sp. Att. For Pikachu, and both used Surf (I picked Pikachu because it doesn't get a STAB boost to complicate things). The difference is, one Pikachu is holding Choice Specs, the other Mystic Water. Which Surf would hit for more?