Whichever is cheaper really. When it comes to RAM, just make sure you have enough of it. The latency and timing is only noticeable in memory-sensitive applications. Gaming is not one of the applicants for it. There may be a few games that is memory-sensitive, but I personally do not know of any. The difference between 1600 and 2133 in gaming is only about 1-3 fps. The increase is very, very little.