What's the advantage of using a third-party plugin over just switching over one of those colorpicking uses to the same system as the other?

(Also, there's a third place where people select color; http://www.dreamwidth.org/manage/circle/add?user=exampleuser&action=subscribe starts off with an interface similar to http://www.dreamwidth.org/manage/circle/edit but allows you to switch to the Hue/Saturation/Brightness picker that's the second level on the http://www.dreamwidth.org/customize/options?group=style chooser.)