It will also depend on the sticks you get, frequency is just part of the equation...performance is a combination of frequency and CL so if you look at 1866/CL9 vs 2133/CL10 - performance wise they will be about the same with a slight nod to 2133 for wider bandwidth (it processes more MB per second than 1866)....on the other hand a 1866/9 vs a 2133/11 or 12, the 1866 will perform better as it takes longer for the 2133 to do a process.....or 1866/10 is much less performance wise than a 2133/9 set.....