Performance wise outside benchmarks probably not see a big diff between the two. Both seem to have low user Problem ratings at newegg.
Plus for HyperX is toggle nand
Neg for HyperX is sandforce controll. This favors ATTO benchmark which is normally what manuf advertize, inflates performance.
My prefernce would be for the Cucial M4 or Samsung 830
Holding off on recommending the 840 until price dropps and It is a little longer in use.