I stash Kona white (bright white) and Kona snow (off white); and also white-on-white designs (also bright white), and use them pretty much interchangably. I decide what works when I'm shopping my stash and piling up fabrics - usually either the bright-whites or the off-whites will look a little weird with the rest of the fabrics and I can tell which should be removed. And if either works, I use whichever one I have the most of!