Reason - on the 1st one there is an interesting interplay of colors between one hue of blue for 2 inner circles and another one for the rest of the dial. It gives a certain depth and visual interest.
The 2nd one is made in one colour and, although nice, imho is more plain and less attractive.
These pictures don't show the difference, although it is there and quite well noticeable.
Pls see better pics here:
www.watchprosite.com