Taylor doesn't compliment Colo as well as Williamson does.
Disagree to a point, Taylor offers all the physicality Williamson does and is quicker. However Taylor is a more aggressive defender than Williamson and will get drawn further up the pitch than where Colo likes to sit. This is evident in the third goal where Colo keeps Tevez onside, but it was probably the right line for the Cb's to be playing in that instance. They haven't had anywhere near the time, game time or training time as Colo and Willo to build an understanding. I firmly believe Taylor is a more talented individual than Williamson and therfore the partnership has more potential but whether the partnership will work well enough to be a top 10 defense in the premier league is yet to be seen.
They had at least half a season together in the 08/09 season. Can't say that went very well either.