I think it's up to the quilter. I've made one using 3.5" and loved it, quilted in the ditch. Made one from country theme fabric using 8.5" blocks, quilted on the diagonal and am really crazy about it. AND have a couple I'm working on in 4.5" blockS. I've just recently found the D9P block pattern and the D4P block pattern and am having fun with both, with the 9 patch my favorite.