Have had both the Mavic Exaliths and the DT Swiss. The Mavics provide slightly better braking I think but the surface colour does wear off, I found it to be quite gradual though and that was through use in all seasons. I haven't had the DT Swiss as long but haven't noticed any degradation in the colour at all.
Have you used the blue pads with the DT Swiss wheels? I think they come with them but some people seem to have got better results with standard black SwissStop.
Have had both the Mavic Exaliths and the DT Swiss. The Mavics provide slightly better braking I think but the surface colour does wear off, I found it to be quite gradual though and that was through use in all seasons. I haven't had the DT Swiss as long but haven't noticed any degradation in the colour at all.