I tend to vacillate on this issue myself, as my XD I have set up with black rear posts and big white front dot, which is the same set up I have on my Para Tac-5. On the other hand, my Para 16-40 has black on black BoMars, and the Gun Blog 9mm has FauxMar rears and a fiber optic front. Rounding out the different sight configurations on guns I’ve owned is my 625 which has black rear posts and a big ol’ HiViz fiber front.
I do know that for accuracy games like Bianchi Cup, I definitely prefer a “black rear posts, black front post” sight arrangement. I feel that it gives finer accuracy control, which is the heart and soul of Bianchi Cup.