in the majority of things the 2133 would win out, even tho the cl 8 would yield a slightly lower latency.
./mem-ns 1866 8
one: 8.57, eight: 12.33
./mem-ns 2133 10
one: 9.38, eight: 12.66
./mem-ns 1866 9
one: 9.65, eight: 13.40
sub timings would come into play, bandwidth, mem controller design, specific apps, etc.
Generally the higher bandwidth would win out in most things.