I read somewhere (and sometime ago) that the 'strongest' sperm to fill a woman is the one she is desiring the most at the time.
So, if a woman is really attracted and wanting a specific man, her body then would do miracles to recept and perhaps become pregnant with that specific sperm material.
So, as it already was said here, it's a man-to-man competition.
A bbc charming man would win over a meek bwc guy...in the same sense that a bwc fierce man would win over a sloppy bbc fella. I guess lol.