The overclocking results are presented in the order of CAS Latency timings.

The first screenshot from each CL testing is from the 1625MHz pair, and the second screenshot is from the 1800MHz pair.

Testing at CL7-7-7-

KHX13000LLK2/2G: 1800MHz @ CL7-7-7-, 2.20V

KHX14400D3K2/2GN: 1800MHz @ CL7-7-7-, 2.20V

Testing at CL8-8-8- 

KHX13000LLK2/2G: 1820MHz @ CL8-8-8-, 2.20V

KHX14400D3K2/2GN: 1840MHz @ CL8-8-8-, 2.20V

Testing at CL9-9-9- 

KHX13000LLK2/2G: 1820MHz @ CL9-9-9-, 2.20V

KHX14400D3K2/2GN: 1900MHz @ CL9-9-9-, 2.20V

Based on our results from memory performance and overclocking, we found that the KHX13000LLK2/2G 1625MHz kit performed slightly better clock-for-clock when compared against the KHX14400K2/2GN 1800MHz kit. This could be due to slightly tighter internal latencies programmed by Kingston's engineers.

Assuming both the KHX13000LLK2/2G and the KHX14400K2/2GN utilize ICs from the same manufacturer, then it would also explain why the former fairs slightly poorer against the latter in terms of maximum frequency overclock.