What would you choose? White herb / Life orb? @Cloyster.~~
These are the details:
Cloyster (M) @Life Orb/White Herb
Trait: Skill Link
EV's: 252 Spe / 252 HP / 4 Atk
Careful Nature: (+SpD -SpA)
Life Orb lowers Cloyster's HP, which will decrease the length of its sweep.
White Herb cancels out the Defense drop, so your Cloyster has more of a chance of surviving.
And also, use Rock Blast over Spike Cannon.