Hello... the difference in ram performance can be measured in Nano second, it takes you 300 milli-seconds to blink, I would prefer Quantity over speed rating, if the prices were the same.
I also would recommend the 16gb beacuse your getting twice the size, just a lower speed though. I have g skill ripjaws x 16gb ddr3 1866 and it is amazing. Really depends on your preference
what im sayin is two stick of 1866 MHz faster than the 4 of 1333 I don't care about size and the 4 are 30 dollars cheaper but I already purchased the 8 gb the 4 stick is 50$ on ebay I bid on an happened to win is why I am asking cause if the 1333 is faster I will return the 8gb
right ill just get 2 more sticks of the 8gb 1866 and have 16 gigs of that thanks guys I knew it sounded like a dumb question just never thought about it lol