Part of it could be that the Mondeo pieces have their optics on the lens (MKI and MKII) were the Contour only has the lens optics on the pre-98s. The ridges in the lens will mess with the lighting and send some of it back to the viewer. Different shapes inside the lamp would also account for differences.
Notice you can't see the Mondeo's bulbs? You can on the 98+ tours.
