I too was on a quest to find a 'good' white ink pad. Tried Staz On, Brilliance 'Moonlight White', the JoAnn brand and Versa Magic 'White Cloud' none gave a consistent white impression.
I am now trying Ranger Adirondack 'Snow Cap' pigment ink pad. It seems to be the best for me so far. My problem is I don't use the white ink often (mostly holiday season) so I think the pad dries out. Even adding reinker doesn't seem to help. My first Staz On white pad dried stuck to the clear plastice inner cover.
Good luck in your search!