Hidden Power with base 60 is rather weak. It's often most useful for those 4x weaknesses (fire, ice, etc. or if your coverage if really really bad).
I think Grass Knot is generally much better. You'll generally want to use it on heavier targets anyway (Tyranitar, Terrakion, Gyarados (especially useful against his mega, since M-Gyara resists fire and is immune to psychic), Rhyperior, Milotic, Cloyster).