All wood will darken over time with UV. There really isn’t much difference in my opinion on these two species. The White Cedar will have a lot more rot resistance than White Pine. Also keep in mind that the lighter you go the more maintenance you are going to have. And definitely do not do a clear of any sort like the water barrier’s that are out there. They are full of wax and will turn your house black quickly. Pay up front for a good quality latex stain made for log homes like Life Line or Sashco Capture.