Do you run both 1D-Xs with the exact same settings? I also experience the blink once upon achieving focus and of course I am quite happy with it. Different configuration settings and corresponding camera usage may still result in different behaviour, but since you are a couple, you should be able to sort this out pretty quickly. If you double-check your configurations are exactly the same and how you use the cameras is exactly the same, does it still come out with different results?
I am just wondering here, because it appears to be quite strange to experience such different results without something actually being different. You should run some tests here and if you do find something strange, it would be a good idea to have CPS see to it.