Easy ... If I had one of every other watercolor in my stash I would find a use for them long before I found a use for the same number of the mottles shown.
I think a large part of each persons answer will be how they intend on using them. The Mottles have other colors introduced and the color change area is fairly large. My favorite style of quiltes are in small - very small pieces, so I have little use for large prints.