Thanks for the responses. I was asking because I can get the PC3-10600 DDR3 1333 (16GB) for quite a bit cheaper than the PC3-12800 DDR3 1600 (16GB) . Both from the same manufacturer.
Not that I'm cheap, but if I'm not really going to see a difference, and I have no over-clocking intentions, I would just buy the cheaper memory.
Well you can't just look at the speed, you also need to look at the timings. A cas8 1333 would be as fast or very close to cas9 1600. You also want to make sure you get 1.5v ram, not 1.65v for that cpu. If they are both cas 9 and the 1333 is $10 or more cheaper, go for it. If the difference is $5, I would get the 1600.