You certainly say that latency doesn't matter?
I disagree, you won't enjoy a 1600/11 RAM. Moreover, Speed doesn't really matter in games, it does matter, but largely in rendering/ 3D developments/ VFX/ etc where the speed decides the overall performance.
See his usage, he's gonna use the PC for simple tasks/ games where speed don't really matter.
So its just a matter of better CL, which'll decide how fast the RAM accesses a cloumn in the module and get it to the memory controller from the time it's requested by the controller.
Also, the 2400 RAM has 1.65V which is not really a point to worry, but the performance will be downscaled automatically to get the voltage to 1.5V. So what's the real difference in buying a higher MHz RAM (the 2400) which will get downscaled and may even perform worse than 1600MHz RAM in games due to Voltage?
IMO, 1600/8, 1866/9, 2133/10 and 2400/11 are all the same for gaming.
Contrary to the most popular of beliefs, memory kits do not work as stated out of the box. The number of times I have walked through a large LAN event and found people playing games on $2000+ water cooled systems, only to find that their kit of DDR3-2400 is actually running at DDR3-1333 astounds me. It is a lot more common than you think, and there is probably someone you know that is a culprit of this. Making sure memory is set at its rated speed is an important part of the process, and as an enthusiast we have a job to make sure that is the case.
Taken from:
http://www.anandtech.com/show/6372/memory-performance-16gb-ddr31333-to-ddr32400-on-ivy-bridge-igp-with-gskill
More reference:
http://www.tomshardware.com/answers/id-2040165/1600-mhz-cl7-2400-mhz-cl10.html
And, the MoBo won't take more than 1600MHz for Haswell refresh, you'd need to enable XMP and manually set the speed in BIOS if you wish to use 2400MHz. 1600MHz will run at defualt w/o such issues.
What I'm trying to establish is not that 2400/10 is not good, it sure is, but it has almost negligible effect on gaming vs a 1600/7 RAM.
Other reference:
https://www.youtube.com/watch?v=dWgzA2C61z4