Now, I understand that 2 sticks > 1 stick, but the Crucial Ballistix Tactical has a CAS Latency of 8 compared to a CAS Latency of 9 for the Kingston RAM. In addition, the Crucial Ballistix Tactical only has a voltage of 1.35V compared to 1.65V for the Kingston XMP Blu Red Series. I'm unsure of which RAM is better, because both has their own advantages. I did some research regarding the voltage of RAM sticks, and it seems that with a AMD CPU (which I plan on buying, AMD FX-6300 to be exact), the voltage makes a smaller difference.
Go for kingston. 2 sticks of 4gb is always better because there is going to be less load on both of the memory sticks, making performance faster. Voltage and latency will be a very minor difference compared to two sticks of ram vs one.