The difference might be 1%. You pick the way.
I think 1866 1.5v is the sweet spot if you are overclocking. 2133 will need 1.65v and that uses up some of the voltage available for overclocking.
Read this on ram scaling: http://www.anandtech.com/show/7364/memory-scaling-on-haswell
go with the 2133 the speed is more important than the CAS when they are each one better and one worse. Honestloy you would almost guaranteed never notice the difference though
The difference might be 1%. You pick the way.
I think 1866 1.5v is the sweet spot if you are overclocking. 2133 will need 1.65v and that uses up some of the voltage available for overclocking.
Read this on ram scaling: http://www.anandtech.com/show/7364/memory-scaling-on-haswell