Cas latency 9 is still pretty good. I doubt their would be any noticeable difference between them in games. I would say the 2133mhz set would be best but I like i said i doubt you would ever notice the diffrence.
I concur with Dunlop0078.
And technically speaking yes, the higher you go with Mhz the higher the Cas latency. But the Mhz boost "makes up" for the lose in latency.