I'm not Joyce, but I've grown both kinds. The white never got as big as the pink, and it finally died out after about 5 years, while the pink one continues on and even got large enough to divide.
For what it's worth, I have noticed that many plants that come in different colors don't seem to be as vigorous if the flowers are white. Although my white Siberian iris far outperform my blue ones. Of course, most blue flowers aren't very vigorous either. I wonder if there's any scientific evidence or reason for that?
