I don't know which of these two sets of RAM are better and I need help deciding which of the two would be best for gaming. I do plan on overclocking the little heathens on a system with an i5-4670k (overclocked as well)
Either is good as long as its supported by your mobo (in this case i guess any Z87 does it), you will not see any difference in gaming tho. Just grab the cheapest, doesn't hurt to grab the 1.5volt either. The 1.65 will work too as XMP profile. Other than that i don't thihnk anyone bothers overclocking ram nowadays. In most cases you won't be able to keep the 1866-2133MHz either if you going for an above mild cpu overclock.