I never take any notice of "measurements" or still pictures. The only true way to objectively rate a cock is to see it in action on video.
For this reason, I believe that the biggest white cock working at the moment is a guy who regularly performs in John Thompson's GGG & 666 series of films. This guy is very pale, has an almost hairless body, and is quite stocky and muscular. In *all* the films I've seen him in, the two off the top of my head are: "Darf Ich Dich Aussaugen?" [GGG] and "Im Bannes Des Spermas" [666]
The peculiar thing about this guy is that you *never* see his face - he always wears a white hockey-mask, and either a black baseball cap or a 3-pointed "Dick Turpin" C18th hat. Anyway, his cock is a huge thick veiny uncut beauty which he uses to full effect on the above two films.
If anyone knows of any bigger white schlong working in current straight porn films, I'd *love* to see it! :o