A guy that I play games with was telling me the other day that 4x4gb is better than running 2x8gb. I always thought it didnt make much of a difference but wanted some outside information from people that prob would know more about it.
i would go for 2X8gb to leave some expansion room in the future and anyway 4 dimms is a rough thing on motherboard... (some reduce speeds, others CL, others run fines, depending on the motherboard quality)
In clear 2X8gb will be my choice unless you have a 16gb 2133mhz kit in 4X4 at 70$ like me...
FYI: 2133Mhz CL11 G.Skill sniper series 1.6V and it runs 2240 CL10 @ 1.65V no problems... (memtest, prime 95, AIDA64 and intel burn test stable)