All depends on the build (CPU/mobo/GPU) and the sticks themselves (i.e. obviously 2133 is faster than 1866 so that's a given, however you need to look at a combination of the CL and the freq, it's a combination that actually determines performance...i.e. as said 2133, yes is faster than 1866, however, if you go buy 2133 sticks with a CL of 11, they will be outperformed (normally) by 1866 sticks running at CL8 or 9