I've tried both types and, have to admit, I liked the 6-piece stack n'whack the best because the triangle pieces added to make the block square give some separation to each kaleidescope.
Fabric choice is VERY important, especially with the OBW. My OBWs looked very much alike, when positioned on the design wall, even though I was very careful to follow the directions in the book on what type of fabric pattern to get. (I'm at work right now, otherwise I'd include a picture.) I've decided to turn my OBW into a S'nW.