Which is used more often, 日没 and 日落 Both 日没 and 日落 express sunset but which one is often more widely used?
If you look at Google hits, you can see a clear distinction:

日落


  About 42,700,000 results


日没


  About 13,500,000 results


I've never heard 日没 in real life, you might hear it more in Japanese.