I think it depends on who I'm making the quilt for.
For a childs quilt I think whimsical.
I also would consider where the quilt will be used.
If you are making the quilt for the living room you may want to consider colors? Nature is lovely in its self and has a lot of neutral colors. And I don't think whimsical would fit in a living room or adult bedroom. I think this is a quilt that will require a lot of thought and just the 'perfect' fabrics and a good pattern.
Personally I would do either or, and would not mix, because the differences would be not be a cohesive finished quilt.
Good luck on your quilt.