You're assumptions are correct and that's why we supply you with both. I favor spherical zebra stripes because I do more "swoopy" stuff than "boxy" stuff. For me, generally speaking, I favor spherical mapping zebras because when my surfaces are curved the single wall of the cube map environment does not span far enough along the surface that I'm trying to analyze continuity and have to do a lot more rotation of my view.
To add to what Mark said, I like the spherical mapping best usually too, because the box is interrupted along all 12 edges, but the sphere is only interrupted at the 2 poles of the pattern on the sphere. I think that makes the spherical mapping easier to look at. In addition to being able to rotate the part within the reflective background, it would also be useful to be able to rotate the background while the part stands still.
You can really get the same effect by using a very busy background on a highly reflective realview appearance. Zebra stripes is really just the realview type reflectivity idealized for analysis. With the reflective realview stuff, I find myself using zebra stripes less and less.
SW has provided some decent tools for analysis of shapes. But, today I was lamenting the poor quality of the curvature display option, to be able to visualize small dimples or ripples on a surface that waffles between concave and convex, but I think that is the worst of it. It would be nice if SW could improve the display of the curvature display option.
Thanks, by the way for the comments about the book. That one is by far my favorite too.