I want to thank all of the commenters yesterday. I heard from lots of new people, some whom I can't reach with an email, so thank you for breaking your silence and commenting. I want to explain the difference between the two quilts the way I would explain it to a group of people choosing fabrics for a quilt.
The first quilt relies on light, medium, and dark values to make the pattern visible so it is using contrast as its key. Working with black and white is a little tricky because the closer you get to an even mix of black and white in a print, the more it looks like grey and it mushes so that the clear black and whites have center stage. This quilt also has the same fabric for the light background all through the quilt, something I rarely do. I felt it might be needed for the contrast to work but in looking at it, I find it a little boring. (I was working with a pattern from Maple Island called Keep Out)
The second quilt uses blend as its key. The closer the blend the more soothing it is to the eye. Earlier in my quilting career I would notice that when couples walked up to the quilts on display that the woman was interested and the man looked bored. The first time I had colorwash/watercolor type quilts on display the men were drawn in and asked lots of questions and the wives tried to pull them away. This circular pattern quilt is a colorwash technique which relies totally on value. You need many, many steps of value to get an even blend where in contrast you usually only need the light, medium and dark values. Black and white is especially hard to do really smooth.
The Strips and Curves pattern relies on a smooth blend to really work well. The more fabrics you have in the run, the smoother the blend will be. If you want to see the rest of the Strips and Curves quilts I have made, go to the right side of my blog and find them under LABELS.