Phase Matching AF:-
Although the tester did not tell what batteries were used in the K-x, I am almost certain that he used NiMHs, with which the AF speed would be slower. No surprise here.
Contrast Detection AF:-
It is yet surprised that the CDAF of the K-x is a bit faster than expected for that particular situation. But in general, I can tell that the K-r's new CDAF software algorithm is way smarter, although the forced zoom-in and out action on display is somehow annoying.
Related:-
My K-r First Hands-ons (Tested Twice)
How to Resolve the K-x Battery Problem?
AA Battery Chargers Fully Compared (4 Models)
Overclocking Your Pentax (AA Battery) DSLR(s)!?
K-m Battery Issue, Solution and Timing Measurbations