Every medium has something unique about it in which its own natural beauty resides. One of the challenges for an artist is to find these qualities of each medium and set them 
working toward one’s task. You draw the thing or paint it, say your subject is a bunch of koi in the koi pond. And what kinds of marks can contribute their own beauty to this image that you represent? Watercolor has veils, and crayons rub the texture of the paper, the watercolor pencils I used above can capture a fingerprint. Oil has its texture and its solid forms.
Every medium is different. Thousands of possible ways to explore. You use your idea, you use the materials, and perhaps you use their effects as well.
Great post!