reason to not update white iPhone 4S to iOS6

We're a family of 4 and just this past weekend took advantage of the 4S price drop -- 2 white phones, 2 black phones. Today, while teaching my folks how to use theirs, we discovered the 2 white iPhone 4S units were still running iOS5 while the 2 black ones had been updated to iOS6 -- this is how Verizon sold them to us, all 4 purchased at the same time in the same transaction!

Is there any reason to not update the white 4S iPhones to iOS6 just like the black ones? I'm pretty sure there's no internal difference, but am feeling a bit paranoid about it now...!