It depends on what you have in mind. There is no general better or worse. What you can say in general, however, is that if you work a lot with sequential reading and writing (compression/decompression, for example), then more Mhz would be better, for random access lower latencies would be better (gaming). But only up to a certain point, because the actual latency is formed from CAS and Mhz.

In this case, even the 6400s would be better in both, though not noticeably for you most likely:
CAS Latency CL
32 (corresponds to ~10.00ns)
Row-to-Column Delay tRCD
39 (corresponds to ~12.19ns)
Row Precharge Time tRP
39 (corresponds to ~12.19ns)
Active-to-Precharge Time tRAS
102 (corresponds to ~31.88ns)

vs. the 6000 CL30:
CAS Latency CL
30 (corresponds to ~10.00ns)
Row-to-Column Delay tRCD
38 (corresponds to ~12.67ns)
Row Precharge Time tRP
38 (corresponds to ~12.67ns)
Active-to-Precharge Time tRAS
96 (corresponds to ~32.00ns)

Depending on cpu and MB I have 6400 cl32 2x32gb